Conjugated Allyl Alcohols through One-Carbon Homologation of Aryl Epoxides

Abstract

Significance: Herein, the synthesis of conjugated allyl alcohols by conversion of various aryl epoxides with a 1:1 mixture of n-BuLi and lithioacetonitrile is reported, furnishing the resulting homologated allyl alcohols in good yields. This protocol shows an unusual regioselectivity, leading to the opposite regioisomers than the strategy reported by Falck (Tetrahedron Lett. 1994, 35, 5449). Comment: Because, besides one equivalent of lithioacetonitrile, one equivalent of n-BuLi is necessary to make the protocol reproducible, and because deprotonation of styrene oxide often shows carbene-like reactivities of the latter, it is assumed that the reaction proceeds via a carbenoid path rather than through an anionic mechanism. CH 3 CN 1. n-BuLi (1.95 equiv) THF, -78 °C 2. (0.95 equiv) -78 to 20 °C, overnight CH 2 OH up to 80% yield R 1 = Me, t-Bu, Ph, Naph, Cl, OMe, dioxolane derivative R 2 = H, Me R 3 = H, Me