US2644849A - Preparation of cyclooctatriene - Google Patents

Description

Patented July 7, 1953 PREPARATION OF CYCLOOCTATRIEN E Louis E. Craig, Washington, N. J., and Irma J. Ressa, Easton, Pa.,assignors to General Aniline & Film Corporation, New York, N. Y., a corporation. of Delaware No Drawing. Application March 14, 1951,

SerialNo. 215,625

Claims. 1 This invention relates to an improved process for preparing cyclooctatriene from cycloootatetraene.

Heretofore, cyclooctatetraene was converted to cyclooctatriene by reaction with lithium in ethyl ether to form an alkali metal adduct of the hydrocarbon, and the latter reacted with methanol to form cyclooctatriene. The reported yield obtained by this method was only 39% of theory. Sodium reacts with cyclooctatetraene in ethanol or methanol to form mainly cyclooctadiene rather than cyclooctatriene. In copending application Serial No. 187,674 of September 29, 1950, of L. E. Craig, cyclooctatetraene is reduced at a temperature of 60 to -33 C. in liquid ammonia with sodium to cyclooctatriene in yields of about 65 to 70% of theory.

We have now discovered that cyclooctatetraene can be converted to cyclooctatriene in yields of 85 to more than 9il% of theory by reaction with an alkali metal and a primary or secondary nitrogen base (i. e., a primary or secondary amine, or an NH heterocyclic base, such as aniline, N methylaniline, N-ethylaniline, piperidine, and the like) in an ether as a reaction medium.

The result obtained according to this invention is especially surprising since, as distinguished from reduction of cyclooctatetraene, to cyclooctatriene with sodium in ammonia in the absence of an ether, such reaction does not occur with sodium in a primary or secondary amine in the absence of an ether.

It is accordingly an object of this invention to provide an improved process for the preparation of cyclooctatriene from cyclooctatetraene, affording substantially higher yields than thos heretofore obtained.

The amount in mols of the primary or secondary nitrogen base employed in the process is preferably in excess of the number of atomic equivalents of hydrogen theoretically required for hydrogenation to cyclooctatriene of the quantity of cyclooctatetraene undergoing reduction. In general, th quantity of the nitrogen base amounts to two to four mols per mol of cyclooctatetraene. The amount of alkali metal used is likewise preferably slightly in excess of the amount theoretically required to reduce the cyclooctatetraene to cyclooctatriene, thus amounting to somewhat more than two atomic equivalents of alkali metal per mol of cyclooctatetraene. An excess of the order of 10% is generally suitable. The ether is preferably employed in an amount exceeding the quantity of nitrogen base and is sufiicient to maintain the liquid reagents in homogenous solution.

Suitable amounts of the ether solvent range, for example, from two to four times the combined amount of nitrogen base and cyclooctatetraene. The preferred reaction temperature for th process of the invention is from 0 to 30 0., although somewhat higher or lower temperatures can be used.

Suitable ethers for the present process are particularly the lower aliphatic ethers, especially diethyl ether and also heterocyclicethers such as dioxane and tetrahydrofuran; Other cyclic and acyclic ethers which are non-reactive toward the other components of the reaction mixture can also be used. Similarly, other primary or secondary nitrogen bases of the aliphatic, alicyclic. aromatic or heterocyclic series can replace those specifically mentioned above.

Since it has been found that 1,3,6-cyclooctatriene is isomerized by alkaline reagents to the corresponding 1,3,5-isomer, the product obtained by the process of this invention is a mixture of the 1,3,5- and 1,3,6-isomers, the relative proportions of the two isomers in the product varying depending upon the extent of isomerization.

The process of our invention is illustrated in the following examples, wherein parts are by weight.

Example 1 21 parts of cyclooctatetraene and 73 parts of N- ethylaniline were dissolved in 250 parts of absolute diethyl ether. The resulting solution was agitated at room temperature (about 25 C.) and 10 parts of metallic sodium were added in small pieces over a period of 2 hours. After agitating for an additional period of 2 hours, all of the sodium metal had undergone reaction. 250 parts of water were slowly added to the reaction mixture, and after separating the organic layer of the mixture from the aqueous layer thereof, the organic layer was washed with dilute hydrochloric acid to remove unreacted amines, then with water, and then dried over a water-absorbent salt (anhydrous magnesium sulfate). Ether was removed by distillation, yielding as a residue a. faintly yellow colored liquid amounting to 19.7 parts. The product was found by polarographic analysis to contain only 1.2% of unreacted cyclooctatetraene, the remainder being cyclooctatriene as indicated by absorption of 3 mols of hydrogen on catalytic hydrogenation. The ultraviolet absorption spectrum of this product indicated it to be a mixture of 1,3,5- and 1,3,6-cyclooctatriene. The yield of cyclooctatriene was 92% of theory.

Example 2 10.1 parts of metallic sodium were added portionwise in small pieces to an agitated solution of 21 parts of cyclooctatetraene and 51 parts of piperidine in 250 parts of diethyl ether, while maintaining the mixture at room temperature (25 0.). After agitating for several hours at the aforesaid temperature until all of the sodium had undergone reaction, 250 parts of water were slowly added, and the reaction product isolated in the manner described in the preceding example. After evaporation of the ether, 18.1 parts of a light yellow residue were obtained, containing 3.3% of cyclooctatetraene, the remainder being a mixture of 135- and 1,3,6-cyclooctatriene as shown by absorption of 3 mols of hydrogen and the ultraviolet absorption spectrum. The yield of cyclooctatriene was 85% of theory.

Example 3 the aliphatic, alicyclic, aromatic or heterocyclic series. When other ethers are employed, such as dioxane or tetrahydrofuran, similar results are' obtained, but the reaction proceeds at a slower rate. Instead of sodium, equivalent amounts of potassium or lithium can be used to produce similar results.

Other variations and modifications which will be obvious to those skilled in the art can be used in the foregoing procedures without departing from the scope or spirit of the invention.

We claim: 1. A process for the production of cyclooctatriene, which comprises reacting cyclooctatetraene with an alkali metal and with at least 2 molecular equivalents of an organic nitrogen base having at least one hydrogen attached to the nitrogen thereof, in solution in an ether at a temperature not substantially exceeding 30 C.

2. A process for the production of cyclooctatriene, which comprises reacting 1 mol of cyclooctatetraene with at least two atomic equivalents of metallic sodium and at least two mols of an organic nitrogen base having at least one hydrogen attached to the nitrogen thereof, in solution in an ether, at a temperature from 0 to 30 C.

3. A process for the production of cyclooctatriene, which comprises reacting 1 mol of cyclooctatetraene with 2 to 2.2 atomic equivalents of metallic sodium and 2 to 4 mols of N-ethylaniline in ethyl ether solution at a temperature of 0 to 30 C.

4. A process for the production of cyclooctatriene, which comprises reacting 1 mol of cyclooctatetraene with 2 to 2.2 atomic equivalents of metallic sodium and 2 to 4 mols of piperidine in ethyl ether solution at a temperature of 0 to 30 C.

5. A process for the production of cyclooctatrlene,which comprises reacting 1 mol of cyclooctatetraene with 2 to 2.2 atomic equivalents of metallic sodium and 2 to 4 mols of aniline in ethyl ether solution at a temperature of 0 to 30 C.

LOUIS E. CRAIG. IRMA J. RESSA.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 2,594,889 Elofson Apr. 29, 1952 OTHER REFERENCES Ziegler et al., Justus Liebigs Annalen der chemie, vol. 567, 1950, p. 41 (publication date March 31, 1950; article received October 28, 1949).

Craig, Chemical Reviews, vol. 49, No. 1, p. 121, August 1951.

Claims (1)

1. A PROCESS FOR THE PRODUCTION OF CYCLOOCTATRIENE, WHICH COMPRISES REACTING CYCLOOCTATETRAENE WITH AN ALKALI METAL AND WITH AT LEAST 2 MOLECULAR EQUIVALENTS OF AN ORGANIC NITROGEN BASE HAVING AT LEAST ONE HYDROGEN ATTACHED TO THE NITROGEN THEREOF, IN SOLUTION IN AN ETHER AT A TEMPERATURE NOT SUBSTANTIALLY EXCEEDING 30* C.