Convenient methods for the synthesis of highly functionalized and naturally occurring chiral allenes

Abstract

A convenient two step procedure to access highly functionalized chiral allenes using chiral N-methylcamphanyl piperazine derivatives is described. In this transformation, chiral propargylamines are obtained in 79-96% yields with up to 99:1 dr by the CuBr catalyzed reactions of chiral piperazine derivatives with 1-alkynes and aldehydes containing functional groups, which are converted into chiral allenes in the presence of zinc bromide, affording the chiral allenes in 59-85% yields and with up to 99% ee. The antifungal agent Sapium japonicum and an allene precursor intermediate for the synthesis of the pheromone of the male dried bean beetle 15 are obtained in 72-78% yields and with up to 98% ee following this methodology.