IL45977A - Process for preparing cis-olefins - Google Patents

Description

PROCESS FOR PREPARING CIS-OLEFINS (HOE 73/F 336) Stereospecific syntheses of olefins according to Wittig's reaction by means of salt-free ylides are already known (see: Angew. Chem. 78 (1966), 677). Such ylide solutions had to be prepared hitherto according to the technically complicated sodium-amide method (Liebigs Ann. Chem. 619, (1958), 10; Angew. Chem. 77 (1965), 609).

The present invention provides an improved process for preparing cis-olefins of the formula H H - R - C = C - R , III wherein R is straight-chain or branched (C^-C^)alkyl or alkenyl and straight-chain or branched alkyl or (C2-C20) alkenyl group both being optionally substituted in 3-position double bound or in farther position relative to the ^I4ehyde-g¾ by hydroxy, lower carbalkoxy or (C C^) acyloxy, which comprises dissolving an alkali metal or alkaline earth metal in a hexaalkylphosphoric acid triamide, adding to the solution obtained a phosphonium salt of the formula Φ Θ R-CH2-P(C6H5)3Br , I and adding to the reaction mixture obtained an aldehyde the formula and isolating the product obtained by known methods.

Suitable alkali metals or alkaline earth metals are preferably lithium, sodium and magnesium, especially potassium, furthermore calcium, strontium and baryum.

The alkyl groups in the hexaalkylphosphoric acid triamide may be identical or different and 1 to 4, especially 1 or 2 carbon atoms. The well-known easily^ obtainable hexamethylphosphoric acid triamide is especially preferred.

The process is generally carried out as follows: Crushed alkali metal or alkaline earth metal is introduced under nitrogen atmosphere into the hexaalkylphosphoric acid triamide while stirring or shaking, whereby the original blue color of the solution turns reddish-brown. For reasons of ¾implicity the dissolution is effected at room temperature, but may be carried out generally at temperatures of from 10 to 80°CV preferably from 15 to 30°C. When the alkaline earth metal or alkali metal has dissolved completely after approximately 1 to 3 hours, an equivalent quantity or optionally an excess of calculated on the metal up to 20 %f/ preferably up to 10 % of a phosphonium salt of formula I, wherein R preferably contains up to 10 carbon atoms, is added to the solution. The phosphonium salts may be obtained by known processes for instance by reacting corresponding ÷ 0<-bromosubstituted compounds with triphenyl phosphine. The phosphonium salt may be added as such or preferably in the form of a suspension in hexamethylphosphoric acid triamide. The quantity of hexamethylphosphoric acid triamide required per milli-mole of phosphonium salt or per milliequivalent of alkali metal or alkaline earth metal is generally in the range from 0.5 to 5 ml or more, preferably from 0.8 to 2 ml. The upper limit is not critical.

An aldehyde of formula II is then added to the ylide solution obtained. In these aldehydes R' preferably contains 2 to 15 carbon atoms and may be substituted (preferably in terminal position by hydroxy, lower carbalkoxy or lower acyloxy, preferably a formyloxy or acetoxy group.

The reaction mixture is stirred at the chosen reaction ^ temperature until the reaction is complete (at room temperature after about 8 to 15 hours). The olefin formed is isolated in known manner, for example by distillation or, in the case of to higher boiling compounds, by pouring on/ice and subsequent extraction.

The aldehyde may as well be prepared in situ by oxidizing the ylide solution, for example by means of dry oxygen.

In this manner symmetric cis-olefins of the formula H H I I R - C = C - R Ilia are obtained, having a degree of purity of more than 95 % according to gaschromatographic and spectroscopic analyses. compounds of the invention They/are valuable intermediates for organic syntheses and a series of these compounds has a pheromone effect on a number of lepidoptera.

The following examples illustrate the invention.

E X A M P L E 11 Preparation of Ylide solution Finely cut potassium was introduced in absolute hexa-methylphosphoric acid triamide under a nitrogen atmosphere. up The dark blue solution obtained heated/after about 15 minutes, turning reddish-brown. After 1 to 3 hours, when the potassium was completely dissolved^ a suspension of an equivalent quantity of a phosphonium salt of formula I in absolute hexamethyl-phosphoric acid triamide was added.

E X A M P L E 2: Preparation of cis-octene (4) A ylide solution was prepared from 2.2 g (55 millimoles) of potassium and 20 g (50 millimoles) of triphenyl-n-butyl ' phosphonium bromide in 100 ml of hexamethylphosphoric acid triamide according to example 1 and 4.0 g (55 millimoles) of butyraldehyde were added. After 12 hours the octene(4) obtained was distilled from the reaction solution. It was. taken up in pentane, the solution washed subsequently with diluted sulfuric acid, sodium hydrogen sulfite and water and dried with sodium sulfate. The pentane was removed from the octene(4) by distilling it over a Vigreux .column. The remaining crude product was distilled.

Boiling point7g0 = 120°C Yield : 4.3 g = 76 % e E X A M P L E 3: Preparation of cis-octja.ne(4) by autoxidation Dry oxygen was passed through an ylide solution pre pared in an analogous manner to example 2. The batch was worked up as in example 2.

Boiling pointy = 120°C Yield: 2.0 g = 70 % E X A P L E 4: Preparation of cis-9-alken¾l^ acetates An ylide solution was prepared from 0.94 g (24 millimoles) of finely cut potassium in about 50 ml of absolute hexamethylphosphoric acid triamide and 24 millimoles of triphenylethyl phosphonium bromide. The dimethylamine formed in this process was removed in vacuo as far as possible while excluding humidity. After stirring for 4 hours 20 millimoles (4.0 g) of 9-acetoxy-nonanal were added while cooling with water, the whole was stirred over night and the reaction mixture was poured on ice water acidified with a small quantity of diluted sulfuric acid.

The unsaturated ester was extracted with n-hexane.

The combined hexane extracts were washed with diluted sulfuric^ acid in order to remove small quantities of hexamethylphos-phoric acid triamide. Unreacted aldehyde was separate'd from the unsaturated ester via the hydrogerysulfite addition compound and triphenylphosphine formed during the reaction via triphenyl-methyl phosphonium iodide. Small quantities of triphenyl y phosphine oxide extracted by n-hexane completely cristallized during the night at about -25°C and were filtered off with suction. After drying the n-hexane was removed in vacuo and the colourless oily residue was distilled. y The yield was 2.2 g (50 %) of cis-9-undecenol-1Aacetate . Boiling pointQ Q1 84°C.

In the same manner a number of other compounds having pheromone effect on various lepidoptera were prepared by varying R, for example, cis-9-dodecenol-1-acetate boiling pointQ ^ 101 - 102°C (R = n-propyl) yield 2.3 g (51 ) This compound has a repellent effect on males of the pine' shoot moth (Evetria buoliana Schiff.) and is the sexual fe attractant of/males of Paralobesia viteana. cis-9-tridecen¾-l-AA/acetate boiling pointQ ^ 97°C (R = n-butyl) yield 2.6 g (54 %) boiling pointQ Q1 102 - 104oC (R = n-pentyl) yield 2.6 g (51 5 This compound is the sexual attractant of females of Spodoptera frugiperda, as well as a component of the pheromone of Adoxophyes orana. cis-9-pentadecenol-1-acetate "boiling pointQ Q^ 118 C (R = n-hexyl) yield 2.8 g (57 %) y E X A M P L E 5: Preparation of cis-l -alkenpl/yfry-acetates ψ These substances were prepared in an analogous manner as in example 4, by using 4.6 g (20 millimoles) of 11-acetoxy-undecanal instead of 9- acetoxynonanal.

The following compounds having a pheromone effect were obtained y o cis- 1-tridecencl77I/-acetate boiling pointQ Q1 : 101 C (R = n-ethyl) yield : 2.5 g (52%) y o cis-11-tetradecen©l-t-acetate boiling pointQ ^ ^:103 C (R = n-propyl) yield : 2.3 g (45%) This compound is the sexual attractant of the females of Argyrotaenia velutinana, Choristoneura rosaceana, Ostrinia nubilalis, Ancylis spectrana, Zeiraplera diviana and a component of the pheromone of Adoxophyses orana. It also has an attracting effect on cabbage moth. cis- -hexadecen¾l- E X A M P L E 7: Preparation of 2-methyl-cis-7-octadecene 0.94 g (24 millimoles) of finely cut potassium in about 50 ml of absolute hexamethylphosphoric acid triamide were tri reacted with 10.92 g (24 millimoles) of isoocty phenyl phos-phonium bromide giving the corresponding ylide, this was then reacted'with 3.8 g (20 millimoles) of n-undecanal giving the olefin. The whole was worked up as in example 4.

The yield was 2 g (37 %) of 2-methyl-cis-7-octadecene, boiling point: 125 to 129°C/0.2 mm Hg.

When reacting this compound with m-chlorb/lDenzoic acid the corresponding cis-epoxide was obtained, the sexual attracant of the great gipsy moth (Lymantria dispar).

E X A M P L E 8: Preparation of cis-9-trans- 2-tetradecadienyolrylracetate 4.0 g of acetoxynonanal was added dropwise to an ylide solution prepared according to example 4 by using (E-3-pen-tenyl)-triphenyl phosphonium bromide. The mixture was stirred for 12 hours at room temperature and worked up as in example 4. y Yield: 2.1 g (43 %) of cis-9-trans- 2-tetradecadienga,ylV acetate, boilin 1g pointQ Q^ 110 to 112oC This compound is the sexual attractant of the females of Plodia interpunctuella, Anagasta kiihniella and Laphygma exigua.

It iSp moreover a component of the pheromone of cadra cutella and prodenia eridiana.

E X A M P L E 9 Preparation of cis-9-unsaturated propionates and butyrates The preparation was carried out as in example 4, but using, instead of the 9-acetoxynonanal, either 3.96 g (20 milli- formyloctyl moles) of 9-oxynony-l- -«-propionate or 4.24 g (20 millimoles) of formyloctyl 9- xynonyl~--butyrate . The following compounds were obtained: cis-9-dodecenyl^/-propionate boiling pointQ>05 9 - 97°C yield 2.83 g (62 %) cis-9-tetradecenyl-/ /-butyrate boiling pointQ>01 118 - 121°C yield 2.97 g (55 %) E X A; M P L E 10 Preparation of 9-unsaturated carboxylic acid methyl esters formyloctanoic The corresponding ylide solutions were reacted with 9—©e-onaR-o-ic acid methyl ester (3.4 g, 20 millimoles) as in example 4.

The following substances were obtained: cis-9-dodecenoic acid methyl ester boiling pointQ>03 82 - 83°C yield 2.08 g (49 %) cis-9-trans-12-tetradecadienoic acid methyl ester boiling pointn nR 97 - 99°C yield 2.34 g (50 )

Claims (3)

HOE 73/F 356 What is claimed is;

1. An improved process for preparing cis-olefins of the formula :& H H Λ R - C = C - R , ' III wherein R is straight-chain or branched (C-j-C^^Jalkyl or alkenyl and straight-chain or branched (CJ-C2Q) alkyl or alkenyl group both being optionally substituted in 3-position or in farther position relative to the €^€%¾ -grO-tt by hydroxy, lower carbalkoxy or (Cj-C^) acyloxy, which comprises dissolving an alkali metal or alkaline earth metal in a hexaalkylphosphoric acid triamide, adding to the solution obtained a phosphonium salt of the formula and adding to the reaction mixture obtained an aldehyde of the formula and isolating the product obtained by known methods.

2. Process as claimed i claim 1 , wherein the metal used is potassium and the hexaalkylphosphorus acid triamide used hexamethylphosphorus acid triamide. 45977/2

3. A process according to clain 1 wherein the aldehyde of Formula II is prepared in situ by introducing oxygen into the Attorneys tor -Applicant