CA1078393A - Method for preparing 2-alkenyl-2-oxazolines - Google Patents
Method for preparing 2-alkenyl-2-oxazolinesInfo
- Publication number
- CA1078393A CA1078393A CA280,956A CA280956A CA1078393A CA 1078393 A CA1078393 A CA 1078393A CA 280956 A CA280956 A CA 280956A CA 1078393 A CA1078393 A CA 1078393A
- Authority
- CA
- Canada
- Prior art keywords
- oxazoline
- formaldehyde
- alpha
- alkyl
- hydroxide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D263/00—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings
- C07D263/02—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings
- C07D263/08—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member
- C07D263/10—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
- C07D263/14—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms with radicals substituted by oxygen atoms
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D263/00—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings
- C07D263/02—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings
- C07D263/08—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member
- C07D263/10—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
- C07D263/12—Heterocyclic compounds containing 1,3-oxazole or hydrogenated 1,3-oxazole rings not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms with radicals containing only hydrogen and carbon atoms
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Heterocyclic Carbon Compounds Containing A Hetero Ring Having Nitrogen And Oxygen As The Only Ring Hetero Atoms (AREA)
Abstract
ABSTRACT
2-Alkenyl-2-oxazolines are prepared by (A) reacting an anhydrous 2-alkyl-2-oxazoline with formaldehyde in a molar ratio of at least 1.5 moles of oxazoline per mole of formaldehyde to form 2-(.alpha.-hydroxymethylalkyl)-2--oxazoline (I), (B) recovering (I) from the reaction product and (C) reacting (I) with a hydroxide of an alkali or alkaline earth metal.
The process of step (A) is conducted at 90°-115°C
and the process of step (C) is conducted at 95°-200°C.
The present process results in higher yields of desired product than the prior art processes that employed either an excess of formaldehyde or equimolar quantities of formaldehyde and 2-alkyl-2-oxazoline in step (A).
2-Alkenyl-2-oxazolines are prepared by (A) reacting an anhydrous 2-alkyl-2-oxazoline with formaldehyde in a molar ratio of at least 1.5 moles of oxazoline per mole of formaldehyde to form 2-(.alpha.-hydroxymethylalkyl)-2--oxazoline (I), (B) recovering (I) from the reaction product and (C) reacting (I) with a hydroxide of an alkali or alkaline earth metal.
The process of step (A) is conducted at 90°-115°C
and the process of step (C) is conducted at 95°-200°C.
The present process results in higher yields of desired product than the prior art processes that employed either an excess of formaldehyde or equimolar quantities of formaldehyde and 2-alkyl-2-oxazoline in step (A).
Description
~078393 The present invention is a process for preparing
2-(-hydroxymethylalkyl)-2-oxazolines and 2-alkenyl-2--oxazolines.
The 2-alkenyl-2-oxazolines are particularly useful compounds due to their difunctionality. Of these, the 2--vinyl- and 2-isopropenyl-2-oxazolines are perhaps two of the more useful compounds due to their reactivity in vinyl polymerizations. 2-Isopropenyl-2-oxazoline, for instance has a reactivity much like an acrylate in vinyl polymeri- ~
zations.
Prior art methods of preparing 2-alkenyl-2- ~--oxazolines have heretofore utilized relatively expensive reagents in multistep processes and the product yield was normally low.
The teachings of U.S. Patent 3,535,332, issued to Runge et al, October 20, 1970, and of French Patent 1,557,954 are of particular interest relative to the instant process.-~oth of these references teach that 2-hydroxyalkyl-2-oxa-zolines can be prepared by reacting a 2-alkyl-2-oxazoline with formaldehyde and that such compounds can be subsequently dehydrated to form the 2-alkenyl-2-oxazolines. In these reactions, the 2-hydroxyalkyl-2-oxazolines were prepared by ~` reacting a 2-alkyl-2-oxazoline with an excess of formalde-hyde even though the ~road teachings indicated that equi-molar amounts of reactants could ~e used. The disclosure in U.S. Patent 3,523,123, issued to Wehrmeister August 4, 1970, is similar in this regard. The dehydration of the 2--hydroxyalkyl-2-oxazolines was thermally and/or catalytically induced. French Patent 1,557,954 is the only reference which in fact shows the preparation of 2-isopropenyl-2-18,036-F -1-.
. 1078393 -oxazoline; a compound which (along with 2-vinyl-2-oxazoline) is unique among other 2-alkenyl-2-oxazolines due to its extremely high reactivity. ~ , The defects of the prior art have been substantially overcome by the present invention which is a process for pre-paring a 2-alkenyl-2-oxazoline comprising the steps of:
(A) reacting an anhydrous 2-alkyl-2-oxazoline with formaldehyde in a molar ratio of at least 1.5 moles of 2--alkyl-2-oxazoline per mole of formaldehyde, thereby forming the 2-(a-hydroxymethylalkyl)-2-oxazoline, (B) recovering the 2-(a-hydroxymethylalkyl)-2-- -oxazoline from the reaction product of step A, and (C) reacting the 2-(a-hydroxymethylalkyl)-2--oxazoline from step B with an alkali or alkaline earth metal hydroxide, thereby forming the 2-alkenyl-2-oxazoline.
r . Steps A and C individually as well as the combin-ation o steps A-C are thought to be novel processes.
Step A
Step A is conducted by reacting an anhydrous or essentially anhydrous 2-alkyl-2-oxazoline with formaldehyde to thus make the corresponding 2-(~-hydroxymethylalkyl)-2--oxazoline.
Any 2-alkyl-2-oxazoline can be used herein so long as the 2-alkyl groups bear replaceable hydrogen on the ~--carbon atom (i.e. adjacent to the oxazoline ring). The oxazoline reactants can bear inert ring substituents (e.g.
alk~l groups) in the 4-and/or 5-ring positions. Preferred reactants correspond to the formula H C- N
18,036-F -2-- wherein R is an alkyl (preferably linear) group of from 1 to about 18 carbon atoms. The most preferred reactants are 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline since these are the reactants leading to 2-vinyl-2-oxazoline and 2-iso-propenyl-2-oxazoline, respectively. Other examples of suitable oxazoline reactants include: 2-propyl-, 2-butyl-, 2-hexyl-, 2-heptyl-, 2-nonyl-, 2-undecyl-, 2-heptadecyl-2-~oxazolines and the corresponding 2-substituted 4-methyl-2--oxazolines, 4-ethyl-2-oxazolines, 4-butyl-2-oxazolines, 4,4--dimethyl-2-oxazolines and 4,5-dimethyl-2-oxazolines.
The yield of the desired 2-(a-hydroxymethyl)-2--oxazoline product is maximized when excess 2-alkyl-2-oxa-zoline is used in the process. Normally, we use at least about 1.5 moles of 2-alkyl-2-oxazoline per mole of formalde-hyde. The preferred ratio of reactants, however, is from about 2 to about 10 moles of oxazoline reactant to formalde-hyde and the most preferred ratio is from about 3 to about S moles of oxazoline reactant per mole of formaldehyde.
In addition to the utilization of excess oxazoline reactant in the process, we have found that product yields are maximized by conducting the reaction under anhydrous ar substantially anhydrous conditions. For this reason, we -prefer to predry the oxazoline reactant (normally with molecular sieves or solid sodium hydroxide) and use a source of formaldehyde that is low in water content. Paraformalde-hyde having a 95 percent or greater formaldehyde content is commercially available and is the preferred formaldehyde source. Formaldehyde per se and other non-aqueous sources of formaldehyde (e.g. trioxane and other polymers of for-maldehyde) are suitable, however.
1~ 036-F -3-~078393 The process may be conducted at any suitable temperature ~hat promotes the reaction and is below the de-composition temperature of the desired product. Satisfactory reaction rates have been observed at temperatures of from about 90 to about 115C and temperatures of from about 95 to abou~ 105C are normally preferred. At these temperatures, reaction times of from about 2 to about 8 hours are conven-tional. Inert organic solvents (e.g., benzene, toluene, etc.) may be used if desired but we prefer to conduct the process without using a solvent.
Step B
The 2-(a-hydroxymethylalkyl)-2-oxazoline may be recovered from the reaction product of Step A by any of several conventional techniques, for example, by solvent extraction or fractional distillation. In those instances where the oxazoline reactant and product are liquids and/or low melting solids, fractional distillation under reduced pressure at a temperature below the decomposition temper-ature of 2-~-hydroxymethylalkyl)-2-oxazoline is normally used. In this manner, the excess oxazoline reactant and water normally codistill and are recovered. The reactan~
oxazoline/water distillate can then be dried and the 2--alkyl-2-oxazoline recycled back into Step A. The 2_l--hydroxymethylalkyl)-2-oxazolines are higher boiling and thus recovered from the distillation as the "pot residues"
which can be used per se in Step C but are preferably further purified (generally by distillation using a falling film still or other conventional techniques) before use.
We have found that the overall yield of the 2--alkenyl-2-oxazoline is maximized when Step B is conducted as soon as practical after Step A.
18,036-F ~4~
.
Step C
In this step, the 2-(a-hydroxymethylalkyl)-2--oxazoline is dehydrated by contacting same with an alkali or alkaline earth metal hydroxide, thereby forming the 2~
-alkenyl-2-oxazoline. This~ reaction may be conducted at any - temperature sufficient to promote the dehydration but we have found satisfactory reaction rates normally occur at temperat~res of from a~out gS to about 200~C under reduced pressure (e.g., from about 10 to about 150 mm.Hg).
Essentially any alkali or alkaline earth metal hydroxide can be used in Step C but the efficiency of the alkali or alkaline earth metal hydroxides to promote the dehydration tends to correlate with the degree of solubllity of the alkali or alkaline earth metal hydroxide in hot water.
That is, the more water soluble the alkali or alkaline earth metal hydroxide is in hot water the more efficient it - appears to be in dehydrating the 2~ hydroxymethylalkyl)--2-oxazoline. Lithium hydroxide, sodium hydroxide, potassium hydroxide and barium hydroxide are the preferred catalysts and sodium hydroxide is most preferred, ~ased upon its efficiency and relative costs.
Step C may be conducted in a batchwise or contin-uous manner and we prefer to conduct it in a continuous manner. In the continuous process, the 2-(a-hydroxymethyl-alkyl)-2-oxazoline is added to the alkali or alkaline earth metal hydroxide catalyst at reaction temperature. The 2--alkenyl-2-oxazoline can-normally be volatilized at the reaction temperatures under reduced pressure and is codis-tilled with water from the reaction vessel. Thus, the 2-~ hydroxymethylalkyl)-2-oxazoline is metered into the 18,036-F -5-reaction vessels at substantially the same rate at which the 2-alkenyl-2-oxazoline/water mixture is removed as over-heads. The 2-alkenyl-2-oxazoline can be conveniently recovered from the 2-alkenyl-2-oxazoline/water solution using conventional solvent extraction techniques.
Inert organic solvents which remain liquid at the reaction temperature may be included in Step C if desired.
However, we find that Step C is preferably conducted either neat or in the presence of a lower alkyl monoether of a polyalkylene glycol. The latter compounds are known to be solvents for the alkali and alkaline earth metal hydroxides and are, therefore, preferred organic solvents for use in this step. This known class of compounds include, for example, the methyl, ethyl, propyl and butyl ethers of diethylene glycol, triethylene glycol, etc. The monomethyl ether of triethylene glycol appears to be the most efficient when sodium hydroxide is used as the catalyst.
EXAMPLE 1 - Preparation of 2-Isopropenyl-2-oxazoline ~-Ethyl-2-oxazoline ~594 g; 6.0 moles) and 9S
; 20 percent paraformaldehyde (63.2 g; 2.0 moles~ were charged to a reaction vessel equipped with a mechanical stirrer and condenser. The reaction mixture was heated to 100C with stirring and maintained under these conditions for 4 hours.
A sample of the reaction mixture was then analyzed by ~apor phase chromatography with the following results: 60.7 -- weight percent 2-ethyl-2-oxazoline; 37.9 weight percent 2--(à-hydroxymethylethyl)-2-oxazoline; and the remaining 1.4 weight percent was not identified. On these data, the - conversion of 2-ethyl-2-oxazoline was 98.5 percent and the the percent yield of 2-(a-hydroxymethylethyl)-2-oxazoline :
18,036-F -6-.. . .
was 96.5 percent. The excess 2-ethyl-2-oxazoline was removed from the reaction mixture by distillation under reduced pressure leaving the desired 2-(a-hydroxymethylethyl)--2-oxazoline as the still bottoms.
Sodium hydroxide beads (60.0 g; 1.5 mole) were - - added to a reaction vessel equipped with a mechanical stirrer, a dropping funnel and a distillation column packed with 1/4 inch (0.64 cm.) glass beads. This materiaI was heated to a pot temperature of approximately 175C at a pressure of 150 mm.Hg. ~o this heated system was added the 2-(a-hydroxy-methylethyl)-2-oxazoline from the above (containing 100 ppm of a polymerization inhibitor) at a rate of approximately 1 g. per minute. A11 volatiles passing through the distil-lation column were collected in a cold trap and analyzed by vapor phase chromatography using 1,2,4-trichlorobenzene as an internal standard. The mixture contained 2.5 weight percent unreacted 2-ethyl-2-oxazoline; 11.7 weight percent water; and 85.8 weight percent 2-isopropenyl-2-oxazoline.
This amounts to a 97.8 percent yield of 2-isopropenyl-2--oxazoline.
Similar high yields were obtained when the dehy-dration was conducted using sodium hydroxide dissolved in the monomethyl ether of triethylene glycol and a-minor ; amount of water. Data obtained on a series of such dehy-drations indicate that the effective life of the sodium hydroxide catalyst was extended by using this material as a reaction medium.
EXAMPLE 2 - Preparation of 2-(~-dodecenyl)-2-oxazoline Using the same ratio of reactants and substantially the same process conditions, 2-lauryl-2-oxazoline was 18,036-F -7-.. ...
. . .
~78393 reacted with paraformaldehyde at 100C for 5 hours. The 2-~-hydroxymethylalkyl)-2-oxazoline product crystallized out of the liquid reaction mixture. The solid product was separated by filtration and recrystallized in n-hexane. The recrystallized product was obtained as a white crystalline solid melting at 64-67C. The yield of recrystallized product was 70 percent, based on formaldehyde. A portion of this recrystallized material (15 g; 0.06 mole) was warmed to a melt and added dropwise to sodium hydroxide beads -10 (20 g.) preheated to a temperature of 175C at 0.5 mm.Hg.
~he 2-(a-dodecenyl)-2-oxazoline was immediately volatilized and was collected in a cold trap cooled with ice water. The product was thus obtained as a liquid boiling at 127~C at 0.03 mm.Hg in 71 percent yield, based on the starting 2--~-hydroxymethyllauryl)-2-oxazoline.
EXAMPLE 3 - Preparation of 2-Vinyl-2-oxazoline Using the same reaction conditions set forth in Example 1, 2-methyl-2-oxazoline was reacted with formalde-hyde, thereby forming 2-hydroxyethyl-2-oxazoli~e in approxi-mately 83 percent distilled yield~ The proauct had a ~oil-ing point of 55-58C at 0.5 mm~HgL Dehydration of the product was likewise performed under conditions similar to Example l. Sodium hydroxide beads (20 g.) were heated to 150C at 150 mm~Hg. To this was added dropwise the 2--hydroxyethyl-2-oxazoline (56 g; 0.49 mole) and the volatiles thus formed collected in a receiver cooled with ice water.
The condensed volatiles were identified as an aqueous solution of 2-vinyl-2-oxazoline which boiled at 83-85C at 150 mm. Hg. No impurities appeared to be present in the aqueous solution of the 2-vinyl-2-oxazoline and the recovered product amounted to a material balance of over 95 percent~
18,036-F -8-- ~o78393 . .
;
EXAMPLE 4 - Preparation of 2-Isopropenyl-2-oxazoline A stainless steel reaction vessel was loaded with paraformaldehyde (96.7 percent) and 2-ethyl-2-oxazoline in a molar ratio of approximately 4 moles of oxazoline per mole of fonmaldehyde. The ~xazoline reactant was predried over 3 A molecular sieves and contained only 490 ppm water.
The reaction mixture was blanketed with dry nitrogen and the system closed. The reaction mixture was heated to 100C and maintained at this temperature for a period of 4.5 hours. The excess 2-ethyl-2-oxazoline was subsequently distilled from the reaction mixture at 20 mm~Hg pressure.
The distillation took two hours and was terminated when the overhead temperature reached 97Co This gave 30 parts by weight of pot residue containing 92 weight percent 2~
; 15 -hydroxymethylethyl)-2-oxazoline and 74.5 parts by weight t of distillate containing 98 weight percent 2-ethyl-2-oxazo-line, 1.5 weight percent 2-(a-hydroxymethylethyl)-2-oxazo- t li~e, 0.52 weight percent water, and a trace of 2-isopro-, penyl-2-oxazoline. About 1.2 parts by weight of the reaction mixture was removed during the course of reaction as samples~
The yield of 2-(-hydroxymethylethyl)-2-oxazoline was thus 94 percent, based on formaldehyde charged and 92 percent based on 2-ethyl-2-oxazoline consumed.
The crude 2 (~-hydroxymethylethyl~ oxazoline was flash distilled in a continuous distillation in which an aliquot of the crude material was heated to distillation tem~erature and thereafter the crude material was added at essentially the same rate at which the distillate was taken overhead. The overhead temperature was 87-97C/2.6-5 mm.Hg.
18,036-F _g_ ~0783g3 Sodium hydroxide beads (43.9 parts by weight) and water (28.9 parts by weight) were charged to a reaction vessel containing a mechanical stirrer, heating means, and distillation apparatus. The mixture was stirred unt~l the sodium hydroxide dissolvèd after which the monomethyl ether of triethylene glycol (150.6 parts by weight) was added.
Pressure over the system was reduced to 40 mm.Hg and the mixture heated to 97C, ca~sing some of the water to distill - overhead at approximately 36C and leaving a ~olution of the sodium hydroxide in the pot.~ The distilled 2-(a-hydroxy-methylethyl)-2-oxazoline was then added to the reaction -flask at a controlled rate by means of a metering pump.
During this addition, 2-isopropenyl-2-oxazoline and water were formed which were simultaneously removed overhead during the reaction at a head temperature of 56-59C and a pot temperature of from 102-108C/39-40 mm.Hg. After the addition of the 2-(a-hydroxymethylethyl)-2-oxazoline was complete, the pot temperature was raised to 150C o~er a twenty minute period to drive out the last of the avail-able 2-isopropenyl-2-oxazoline. The water-white clear distillate was analyzed by vapor phase chromatography usin~
1,~,4-trichlorobenzene as an internal standard. This analy- -sis showed the distillate to be 83.9 weight percent 2-iso-propenyl-2-oxazoline, 15.6 weight percent water (by Karl Fischer analysis) and 0.28 weight percent 2-ethyl-2-oxazoline.
This represents a 97.1 percent yield of 2-isopropenyl-2-oxa-zoline based on the 2-(a-hydroxymethylethyl)-2-oxazoline charged.
The products in the above reactions were also identified by infrared and nuclear magnetic resonance spectroscopy.
18,036-F -10-Other 2-alkenyl-2-oxazolines could be similarly prepared using the appropriate 2-alkyl-2-oxazoline and formaldehyce reactants as et forth above.
~ .~
~' .
.
.
' 18,036-F -11-.: , . ,: . .
The 2-alkenyl-2-oxazolines are particularly useful compounds due to their difunctionality. Of these, the 2--vinyl- and 2-isopropenyl-2-oxazolines are perhaps two of the more useful compounds due to their reactivity in vinyl polymerizations. 2-Isopropenyl-2-oxazoline, for instance has a reactivity much like an acrylate in vinyl polymeri- ~
zations.
Prior art methods of preparing 2-alkenyl-2- ~--oxazolines have heretofore utilized relatively expensive reagents in multistep processes and the product yield was normally low.
The teachings of U.S. Patent 3,535,332, issued to Runge et al, October 20, 1970, and of French Patent 1,557,954 are of particular interest relative to the instant process.-~oth of these references teach that 2-hydroxyalkyl-2-oxa-zolines can be prepared by reacting a 2-alkyl-2-oxazoline with formaldehyde and that such compounds can be subsequently dehydrated to form the 2-alkenyl-2-oxazolines. In these reactions, the 2-hydroxyalkyl-2-oxazolines were prepared by ~` reacting a 2-alkyl-2-oxazoline with an excess of formalde-hyde even though the ~road teachings indicated that equi-molar amounts of reactants could ~e used. The disclosure in U.S. Patent 3,523,123, issued to Wehrmeister August 4, 1970, is similar in this regard. The dehydration of the 2--hydroxyalkyl-2-oxazolines was thermally and/or catalytically induced. French Patent 1,557,954 is the only reference which in fact shows the preparation of 2-isopropenyl-2-18,036-F -1-.
. 1078393 -oxazoline; a compound which (along with 2-vinyl-2-oxazoline) is unique among other 2-alkenyl-2-oxazolines due to its extremely high reactivity. ~ , The defects of the prior art have been substantially overcome by the present invention which is a process for pre-paring a 2-alkenyl-2-oxazoline comprising the steps of:
(A) reacting an anhydrous 2-alkyl-2-oxazoline with formaldehyde in a molar ratio of at least 1.5 moles of 2--alkyl-2-oxazoline per mole of formaldehyde, thereby forming the 2-(a-hydroxymethylalkyl)-2-oxazoline, (B) recovering the 2-(a-hydroxymethylalkyl)-2-- -oxazoline from the reaction product of step A, and (C) reacting the 2-(a-hydroxymethylalkyl)-2--oxazoline from step B with an alkali or alkaline earth metal hydroxide, thereby forming the 2-alkenyl-2-oxazoline.
r . Steps A and C individually as well as the combin-ation o steps A-C are thought to be novel processes.
Step A
Step A is conducted by reacting an anhydrous or essentially anhydrous 2-alkyl-2-oxazoline with formaldehyde to thus make the corresponding 2-(~-hydroxymethylalkyl)-2--oxazoline.
Any 2-alkyl-2-oxazoline can be used herein so long as the 2-alkyl groups bear replaceable hydrogen on the ~--carbon atom (i.e. adjacent to the oxazoline ring). The oxazoline reactants can bear inert ring substituents (e.g.
alk~l groups) in the 4-and/or 5-ring positions. Preferred reactants correspond to the formula H C- N
18,036-F -2-- wherein R is an alkyl (preferably linear) group of from 1 to about 18 carbon atoms. The most preferred reactants are 2-methyl-2-oxazoline and 2-ethyl-2-oxazoline since these are the reactants leading to 2-vinyl-2-oxazoline and 2-iso-propenyl-2-oxazoline, respectively. Other examples of suitable oxazoline reactants include: 2-propyl-, 2-butyl-, 2-hexyl-, 2-heptyl-, 2-nonyl-, 2-undecyl-, 2-heptadecyl-2-~oxazolines and the corresponding 2-substituted 4-methyl-2--oxazolines, 4-ethyl-2-oxazolines, 4-butyl-2-oxazolines, 4,4--dimethyl-2-oxazolines and 4,5-dimethyl-2-oxazolines.
The yield of the desired 2-(a-hydroxymethyl)-2--oxazoline product is maximized when excess 2-alkyl-2-oxa-zoline is used in the process. Normally, we use at least about 1.5 moles of 2-alkyl-2-oxazoline per mole of formalde-hyde. The preferred ratio of reactants, however, is from about 2 to about 10 moles of oxazoline reactant to formalde-hyde and the most preferred ratio is from about 3 to about S moles of oxazoline reactant per mole of formaldehyde.
In addition to the utilization of excess oxazoline reactant in the process, we have found that product yields are maximized by conducting the reaction under anhydrous ar substantially anhydrous conditions. For this reason, we -prefer to predry the oxazoline reactant (normally with molecular sieves or solid sodium hydroxide) and use a source of formaldehyde that is low in water content. Paraformalde-hyde having a 95 percent or greater formaldehyde content is commercially available and is the preferred formaldehyde source. Formaldehyde per se and other non-aqueous sources of formaldehyde (e.g. trioxane and other polymers of for-maldehyde) are suitable, however.
1~ 036-F -3-~078393 The process may be conducted at any suitable temperature ~hat promotes the reaction and is below the de-composition temperature of the desired product. Satisfactory reaction rates have been observed at temperatures of from about 90 to about 115C and temperatures of from about 95 to abou~ 105C are normally preferred. At these temperatures, reaction times of from about 2 to about 8 hours are conven-tional. Inert organic solvents (e.g., benzene, toluene, etc.) may be used if desired but we prefer to conduct the process without using a solvent.
Step B
The 2-(a-hydroxymethylalkyl)-2-oxazoline may be recovered from the reaction product of Step A by any of several conventional techniques, for example, by solvent extraction or fractional distillation. In those instances where the oxazoline reactant and product are liquids and/or low melting solids, fractional distillation under reduced pressure at a temperature below the decomposition temper-ature of 2-~-hydroxymethylalkyl)-2-oxazoline is normally used. In this manner, the excess oxazoline reactant and water normally codistill and are recovered. The reactan~
oxazoline/water distillate can then be dried and the 2--alkyl-2-oxazoline recycled back into Step A. The 2_l--hydroxymethylalkyl)-2-oxazolines are higher boiling and thus recovered from the distillation as the "pot residues"
which can be used per se in Step C but are preferably further purified (generally by distillation using a falling film still or other conventional techniques) before use.
We have found that the overall yield of the 2--alkenyl-2-oxazoline is maximized when Step B is conducted as soon as practical after Step A.
18,036-F ~4~
.
Step C
In this step, the 2-(a-hydroxymethylalkyl)-2--oxazoline is dehydrated by contacting same with an alkali or alkaline earth metal hydroxide, thereby forming the 2~
-alkenyl-2-oxazoline. This~ reaction may be conducted at any - temperature sufficient to promote the dehydration but we have found satisfactory reaction rates normally occur at temperat~res of from a~out gS to about 200~C under reduced pressure (e.g., from about 10 to about 150 mm.Hg).
Essentially any alkali or alkaline earth metal hydroxide can be used in Step C but the efficiency of the alkali or alkaline earth metal hydroxides to promote the dehydration tends to correlate with the degree of solubllity of the alkali or alkaline earth metal hydroxide in hot water.
That is, the more water soluble the alkali or alkaline earth metal hydroxide is in hot water the more efficient it - appears to be in dehydrating the 2~ hydroxymethylalkyl)--2-oxazoline. Lithium hydroxide, sodium hydroxide, potassium hydroxide and barium hydroxide are the preferred catalysts and sodium hydroxide is most preferred, ~ased upon its efficiency and relative costs.
Step C may be conducted in a batchwise or contin-uous manner and we prefer to conduct it in a continuous manner. In the continuous process, the 2-(a-hydroxymethyl-alkyl)-2-oxazoline is added to the alkali or alkaline earth metal hydroxide catalyst at reaction temperature. The 2--alkenyl-2-oxazoline can-normally be volatilized at the reaction temperatures under reduced pressure and is codis-tilled with water from the reaction vessel. Thus, the 2-~ hydroxymethylalkyl)-2-oxazoline is metered into the 18,036-F -5-reaction vessels at substantially the same rate at which the 2-alkenyl-2-oxazoline/water mixture is removed as over-heads. The 2-alkenyl-2-oxazoline can be conveniently recovered from the 2-alkenyl-2-oxazoline/water solution using conventional solvent extraction techniques.
Inert organic solvents which remain liquid at the reaction temperature may be included in Step C if desired.
However, we find that Step C is preferably conducted either neat or in the presence of a lower alkyl monoether of a polyalkylene glycol. The latter compounds are known to be solvents for the alkali and alkaline earth metal hydroxides and are, therefore, preferred organic solvents for use in this step. This known class of compounds include, for example, the methyl, ethyl, propyl and butyl ethers of diethylene glycol, triethylene glycol, etc. The monomethyl ether of triethylene glycol appears to be the most efficient when sodium hydroxide is used as the catalyst.
EXAMPLE 1 - Preparation of 2-Isopropenyl-2-oxazoline ~-Ethyl-2-oxazoline ~594 g; 6.0 moles) and 9S
; 20 percent paraformaldehyde (63.2 g; 2.0 moles~ were charged to a reaction vessel equipped with a mechanical stirrer and condenser. The reaction mixture was heated to 100C with stirring and maintained under these conditions for 4 hours.
A sample of the reaction mixture was then analyzed by ~apor phase chromatography with the following results: 60.7 -- weight percent 2-ethyl-2-oxazoline; 37.9 weight percent 2--(à-hydroxymethylethyl)-2-oxazoline; and the remaining 1.4 weight percent was not identified. On these data, the - conversion of 2-ethyl-2-oxazoline was 98.5 percent and the the percent yield of 2-(a-hydroxymethylethyl)-2-oxazoline :
18,036-F -6-.. . .
was 96.5 percent. The excess 2-ethyl-2-oxazoline was removed from the reaction mixture by distillation under reduced pressure leaving the desired 2-(a-hydroxymethylethyl)--2-oxazoline as the still bottoms.
Sodium hydroxide beads (60.0 g; 1.5 mole) were - - added to a reaction vessel equipped with a mechanical stirrer, a dropping funnel and a distillation column packed with 1/4 inch (0.64 cm.) glass beads. This materiaI was heated to a pot temperature of approximately 175C at a pressure of 150 mm.Hg. ~o this heated system was added the 2-(a-hydroxy-methylethyl)-2-oxazoline from the above (containing 100 ppm of a polymerization inhibitor) at a rate of approximately 1 g. per minute. A11 volatiles passing through the distil-lation column were collected in a cold trap and analyzed by vapor phase chromatography using 1,2,4-trichlorobenzene as an internal standard. The mixture contained 2.5 weight percent unreacted 2-ethyl-2-oxazoline; 11.7 weight percent water; and 85.8 weight percent 2-isopropenyl-2-oxazoline.
This amounts to a 97.8 percent yield of 2-isopropenyl-2--oxazoline.
Similar high yields were obtained when the dehy-dration was conducted using sodium hydroxide dissolved in the monomethyl ether of triethylene glycol and a-minor ; amount of water. Data obtained on a series of such dehy-drations indicate that the effective life of the sodium hydroxide catalyst was extended by using this material as a reaction medium.
EXAMPLE 2 - Preparation of 2-(~-dodecenyl)-2-oxazoline Using the same ratio of reactants and substantially the same process conditions, 2-lauryl-2-oxazoline was 18,036-F -7-.. ...
. . .
~78393 reacted with paraformaldehyde at 100C for 5 hours. The 2-~-hydroxymethylalkyl)-2-oxazoline product crystallized out of the liquid reaction mixture. The solid product was separated by filtration and recrystallized in n-hexane. The recrystallized product was obtained as a white crystalline solid melting at 64-67C. The yield of recrystallized product was 70 percent, based on formaldehyde. A portion of this recrystallized material (15 g; 0.06 mole) was warmed to a melt and added dropwise to sodium hydroxide beads -10 (20 g.) preheated to a temperature of 175C at 0.5 mm.Hg.
~he 2-(a-dodecenyl)-2-oxazoline was immediately volatilized and was collected in a cold trap cooled with ice water. The product was thus obtained as a liquid boiling at 127~C at 0.03 mm.Hg in 71 percent yield, based on the starting 2--~-hydroxymethyllauryl)-2-oxazoline.
EXAMPLE 3 - Preparation of 2-Vinyl-2-oxazoline Using the same reaction conditions set forth in Example 1, 2-methyl-2-oxazoline was reacted with formalde-hyde, thereby forming 2-hydroxyethyl-2-oxazoli~e in approxi-mately 83 percent distilled yield~ The proauct had a ~oil-ing point of 55-58C at 0.5 mm~HgL Dehydration of the product was likewise performed under conditions similar to Example l. Sodium hydroxide beads (20 g.) were heated to 150C at 150 mm~Hg. To this was added dropwise the 2--hydroxyethyl-2-oxazoline (56 g; 0.49 mole) and the volatiles thus formed collected in a receiver cooled with ice water.
The condensed volatiles were identified as an aqueous solution of 2-vinyl-2-oxazoline which boiled at 83-85C at 150 mm. Hg. No impurities appeared to be present in the aqueous solution of the 2-vinyl-2-oxazoline and the recovered product amounted to a material balance of over 95 percent~
18,036-F -8-- ~o78393 . .
;
EXAMPLE 4 - Preparation of 2-Isopropenyl-2-oxazoline A stainless steel reaction vessel was loaded with paraformaldehyde (96.7 percent) and 2-ethyl-2-oxazoline in a molar ratio of approximately 4 moles of oxazoline per mole of fonmaldehyde. The ~xazoline reactant was predried over 3 A molecular sieves and contained only 490 ppm water.
The reaction mixture was blanketed with dry nitrogen and the system closed. The reaction mixture was heated to 100C and maintained at this temperature for a period of 4.5 hours. The excess 2-ethyl-2-oxazoline was subsequently distilled from the reaction mixture at 20 mm~Hg pressure.
The distillation took two hours and was terminated when the overhead temperature reached 97Co This gave 30 parts by weight of pot residue containing 92 weight percent 2~
; 15 -hydroxymethylethyl)-2-oxazoline and 74.5 parts by weight t of distillate containing 98 weight percent 2-ethyl-2-oxazo-line, 1.5 weight percent 2-(a-hydroxymethylethyl)-2-oxazo- t li~e, 0.52 weight percent water, and a trace of 2-isopro-, penyl-2-oxazoline. About 1.2 parts by weight of the reaction mixture was removed during the course of reaction as samples~
The yield of 2-(-hydroxymethylethyl)-2-oxazoline was thus 94 percent, based on formaldehyde charged and 92 percent based on 2-ethyl-2-oxazoline consumed.
The crude 2 (~-hydroxymethylethyl~ oxazoline was flash distilled in a continuous distillation in which an aliquot of the crude material was heated to distillation tem~erature and thereafter the crude material was added at essentially the same rate at which the distillate was taken overhead. The overhead temperature was 87-97C/2.6-5 mm.Hg.
18,036-F _g_ ~0783g3 Sodium hydroxide beads (43.9 parts by weight) and water (28.9 parts by weight) were charged to a reaction vessel containing a mechanical stirrer, heating means, and distillation apparatus. The mixture was stirred unt~l the sodium hydroxide dissolvèd after which the monomethyl ether of triethylene glycol (150.6 parts by weight) was added.
Pressure over the system was reduced to 40 mm.Hg and the mixture heated to 97C, ca~sing some of the water to distill - overhead at approximately 36C and leaving a ~olution of the sodium hydroxide in the pot.~ The distilled 2-(a-hydroxy-methylethyl)-2-oxazoline was then added to the reaction -flask at a controlled rate by means of a metering pump.
During this addition, 2-isopropenyl-2-oxazoline and water were formed which were simultaneously removed overhead during the reaction at a head temperature of 56-59C and a pot temperature of from 102-108C/39-40 mm.Hg. After the addition of the 2-(a-hydroxymethylethyl)-2-oxazoline was complete, the pot temperature was raised to 150C o~er a twenty minute period to drive out the last of the avail-able 2-isopropenyl-2-oxazoline. The water-white clear distillate was analyzed by vapor phase chromatography usin~
1,~,4-trichlorobenzene as an internal standard. This analy- -sis showed the distillate to be 83.9 weight percent 2-iso-propenyl-2-oxazoline, 15.6 weight percent water (by Karl Fischer analysis) and 0.28 weight percent 2-ethyl-2-oxazoline.
This represents a 97.1 percent yield of 2-isopropenyl-2-oxa-zoline based on the 2-(a-hydroxymethylethyl)-2-oxazoline charged.
The products in the above reactions were also identified by infrared and nuclear magnetic resonance spectroscopy.
18,036-F -10-Other 2-alkenyl-2-oxazolines could be similarly prepared using the appropriate 2-alkyl-2-oxazoline and formaldehyce reactants as et forth above.
~ .~
~' .
.
.
' 18,036-F -11-.: , . ,: . .
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for preparing a 2-alkenyl-2-oxa-zoline comprising the steps of:
(A) reacting an anhydrous 2-alkyl-2-oxazoline with formaldehyde in a molar ratio of at least 1.5 moles of 2-alkyl-2-oxazoline per mole of formaldehyde, thereby form-ing the 2-(.alpha.-hydroxymethylalkyl)-2-oxazoline, (B) recovering the 2-(.alpha.-hydroxymethylalkyl)-2--oxazoline from the reaction product of Step A, and (C) reacting the 2-(.alpha.-hydroxymethylalkyl)-2--oxazoline from step B with an alkali or alkaline earth metal hydroxide, thereby forming the 2-alkenyl-2-oxazoline.
(A) reacting an anhydrous 2-alkyl-2-oxazoline with formaldehyde in a molar ratio of at least 1.5 moles of 2-alkyl-2-oxazoline per mole of formaldehyde, thereby form-ing the 2-(.alpha.-hydroxymethylalkyl)-2-oxazoline, (B) recovering the 2-(.alpha.-hydroxymethylalkyl)-2--oxazoline from the reaction product of Step A, and (C) reacting the 2-(.alpha.-hydroxymethylalkyl)-2--oxazoline from step B with an alkali or alkaline earth metal hydroxide, thereby forming the 2-alkenyl-2-oxazoline.
2. The process of Claim 1 wherein said 2-alkyl--2-oxazoline corresponds to the formula:
wherein R is alkyl of from 1 to about 18 carbon atoms having replaceable hydrogen on the .alpha.-carbon atom.
wherein R is alkyl of from 1 to about 18 carbon atoms having replaceable hydrogen on the .alpha.-carbon atom.
3. The process of Claim 2 wherein R is a linear alkyl group.
4. The process of Claim 3 wherein R is methyl or ethyl.
5. The process of Claim 1 wherein the molar ratio of oxazoline to formaldehyde is from 2 to 10.
6. The process of Claim 5 wherein the molar ratio is from 3 to 5.
7. The process of Claim 1 wherein the reaction temperature in step A is from 90° to 115°C.
8. The process of Claim 7 wherein the reaction temperature of step A is from 95° to 105°C.
9. The process of Claim 1 wherein the alkali or alkaline earth metal hydroxide is sodium hydroxide, potassium hydroxide, lithium hydroxide or barium hydroxide and the reaction temperature of step C is from 95° to 200°C.
10. The process of Claim 9 wherein the alkali or alkaline earth metal hydroxide is sodium hydroxide.
11. The process of Claim 10 wherein step C is conducted in the absence of a solvent or in the presence of a lower alkyl monoether of a polyalkylene glycol.
12. The process of Claim 11 wherein said lower alkyl monoether of a polyalkylene glycol is the monomethyl ether of triethylene glycol.
13. The process of Claim 1 comprising the steps of:
(A) reacting anhydrous 2-ethyl-2-oxazoline with paraformaldehyde, having a formaldehyde content of at least about 95 weight percent, in a molar ratio of from 3 to 5 moles of 2-ethyl-2-oxazoline per mole of formaldehyde at a reaction temperature of from 95° to 105°C, thereby forming 2-(.alpha.-hydroxymethylethyl)-2-oxazoline, (B) recovering the 2-(.alpha.-hydroxymethylethyl)-2--oxazoline from the reaction product of step A by fractional distillation, and (C) reacting the 2-(.alpha.-hydroxymethylethyl)-2--oxazoline from step B with sodium hydroxide dissolved in an aqueous solution of the monomethyl ether of triethylene glycol at a reaction temperature of from 100° to 105°C
under reduced pressure, thereby forming 2-isopropenyl-2--oxazoline which is distilled from the reaction mixture essentially at the rate it is formed.
(A) reacting anhydrous 2-ethyl-2-oxazoline with paraformaldehyde, having a formaldehyde content of at least about 95 weight percent, in a molar ratio of from 3 to 5 moles of 2-ethyl-2-oxazoline per mole of formaldehyde at a reaction temperature of from 95° to 105°C, thereby forming 2-(.alpha.-hydroxymethylethyl)-2-oxazoline, (B) recovering the 2-(.alpha.-hydroxymethylethyl)-2--oxazoline from the reaction product of step A by fractional distillation, and (C) reacting the 2-(.alpha.-hydroxymethylethyl)-2--oxazoline from step B with sodium hydroxide dissolved in an aqueous solution of the monomethyl ether of triethylene glycol at a reaction temperature of from 100° to 105°C
under reduced pressure, thereby forming 2-isopropenyl-2--oxazoline which is distilled from the reaction mixture essentially at the rate it is formed.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US69909176A | 1976-06-23 | 1976-06-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078393A true CA1078393A (en) | 1980-05-27 |
Family
ID=24807886
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,956A Expired CA1078393A (en) | 1976-06-23 | 1977-06-20 | Method for preparing 2-alkenyl-2-oxazolines |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1078393A (en) |
| GB (1) | GB1584684A (en) |
-
1977
- 1977-06-20 CA CA280,956A patent/CA1078393A/en not_active Expired
- 1977-06-20 GB GB2576377A patent/GB1584684A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1584684A (en) | 1981-02-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1102352A (en) | Making nitrodiarylamines | |
| EP0000144B1 (en) | Process for preparing 2-isocyanatoalkyl esters of unsaturated carboxylic acids | |
| EP0147379B1 (en) | Making nitrodiarylamines | |
| US4123450A (en) | Process for preparing alkyl isocyanates | |
| JPS5829943B2 (en) | Method for producing diphenylmethane dicarbamate and polymethylene polyphenyl carbamate | |
| US4376861A (en) | Method for preparing 2-alkenyl-2-oxazolines | |
| CA1214167A (en) | Process for preparing cyclic n-vinylacylamines | |
| CA1078393A (en) | Method for preparing 2-alkenyl-2-oxazolines | |
| US5103035A (en) | Process for preparing bis(alkylphenyl)pentaerythritol diphosphites | |
| KR870001929B1 (en) | Process for preparation of 1,3-dialkyl-2-imidazolidinone | |
| MXPA99001054A (en) | Processes for preparing indeno[1,2-e][1,3,4]oxadiazine-dicarboxylates | |
| CA1246588A (en) | Process for preparing substituted oxazolines | |
| US4514339A (en) | Process for preparing alkyl isocyanates | |
| US3226439A (en) | Polyhalogenated alkyl imines and hydrazones and method of preparation | |
| CA1224493A (en) | Process for making nitrodiarylamines | |
| US3678065A (en) | Production of hydroxymethyl vinyl oxazoline | |
| US4169208A (en) | Process for producing unsaturated quaternary ammonium salt | |
| US4876337A (en) | Method and apparatus for the preparation of cyanoalkyl-alkoxysilanes | |
| US3962270A (en) | Process for preparing 2-vinyl oxazolines | |
| US2840566A (en) | Preparation of nu-vinyl ethylene urea compounds | |
| NO156610B (en) | Silanes. | |
| STEWART et al. | Addition Reactions of Atroponitrile (α-Cyanostyrene) 1, 2 | |
| JPS6296493A (en) | Synthesis of tricyclazole | |
| JPS63503063A (en) | Method for producing methyl isocyanate | |
| JPS5924977B2 (en) | Method for producing 2-alkenyl-2-oxazoline |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |