Syntheses of Isoprenoids by Telomerizations. IX. Stereoselectivity of Telomers and the Effect of Telogens in Anionic Telomerizations Using Secondary Amines

Abstract

Abstract The stereoselectivity of the telomers and the effect of the telogens in the anionic telomerizations of isoprene with secondary amines were investigated. Dimethyl-, diethyl-, di-n-propy-1, diisopropyl-, and methylphenyl-amines, pyrrolidine, morpholine, and piperidine were used as the telogens. The ratio of N,N-dialkyl(3,7-dimethyl-2,6-octadienyl)amine(2A) to N,N-dialkyl(2-isopropenyl-5-methyl-4-hexenyl)amine(2B), which were obtained in these reactions, was varied with the sort of secondary amines, the yield of the telomers was found to be dependent on the acidity of the secondary amines. Moreover, 2A, which was the main component of the n=2 telomers, was confirmed to have a cis-configuration—that is, N,N-dialkylnerylamine. However, the n=1 telomer of myrcene with secondary amine was N,N-dialkylgeranylamine. These results were interpreted in terms of the stability of the cyclic intermediate of the carbanions.