One-Flask, Regiospecific Conversions of Allylic Alcohols into Two-Carbon-Extended, Conjugated Dienoate Esters. Use of a New Sulfinyl Orthoester

Article abstract of DOI:10.1021/jo00025a008

Sixteen differently substituted primary and secondary allylic alcohols are shown to react with sulfinyl orthoacetate 1 at 100 deg C sequentially via a <3,3> sigmatropic rearrangement and then a β-elimination of benzenesulfenic acid to form conjugated dienoate esters 5-13 in 45-95percent yields.This one-flask, intramolecular carbon-carbon bond-forming process represents a simple and convenient method for regiospecific γ-attachment of a two-carbon (ethoxycarbonyl)methylene unit via the synthetic equivalent of an S_N2' process.Two examples are given in which rationally designed dienoates 20 and 24, prepared via this one-flask process and carrying a pendant alkene unit, undergo intramolecular 2+4 cycloaddition producing bicyclic cyclohexenes 21 and 25.