A Practical, Stereoselective Synthesis of (E)- and (Z)-2-Bromo-2-pentenes

Abstract

A short, stereoselective preparation of (E)-2-bromo-2-pentene and (Z)-2-bromo-2-pentene is described starting from trans-2-methyl-2-pentenoic acid.

Notes

The metal-halogen exchange reaction is a well-known method for preparing organolithium compounds: Wakefield, B. J. In Organolithium Methods; Academic: London, 1988; pp 21–52.

For example, sequential treatment of 1c with tert-BuLi (2 equiv), MgBr₂, and aldehyde 6 afforded, in good yield, the desired adduct 7, which was converted to the bis(tetrahydrofuran) subunit 8 of asteltoxin: Kim H. Cha J. K. unpublished results.¹