ONE-FLASK, REGIOSPECIFIC CONVERSIONS OF ALLYLIC ALCOHOLS INTO 2-CARBON-EXTENDED, CONJUGATED DIENOATE ESTERS - USE OF A NEW SULFINYL ORTHOESTER

Sixteen differently substituted primary and secondary allylic alcohols are shown to react with sulfinyl orthoacetate 1 at 100-degrees-C sequentially via a [3,3] sigmatropic rearrangement and then a beta-elimination of benzenesulfenic acid to form conjugated dienoate esters 5-13 in 45-95% yields. This one-flask, intramolecular carbon-carbon bond-forming process represents a simple and convenient method for regiospecific gamma-attachment of a two-carbon (ethoxycarbonyl)methylene unit via the synthetic equivalent of an S(N)2' 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.