Thermodynamic and kinetic control in the reaction of carboethoxymethylene- triphenylphosphorane and ethyl lithiotrimethylsilylacetate with 2- (t-butyldimethylsilyloxy)cycloalkanones.

Abstract

The reaction of 2-t-butyldimethylsilyloxy cycloalkanones (5,6 and 7 membered rings) with carboethoxymethylenetriphenylphosphorane gives almost exclusively the E isomeric Wittig products, whereas reaction with ethyl lithiotrimethylsilylacetate gives predominantly the Z isomers. The Z products show the methine proton at ca. 5.5 ppm, an unusually large chemical shift for this type of proton.