THERMODYNAMIC AND KINETIC CONTROL IN THE REACTION OF CARBOETHOXYMETHYLENETRIPHENYLPHOSPHORANE AND ETHYL LITHIOTRIMETHYLSILYLACETATE WITH 2-(t-BUTYLDIMETHYLSILYLOXY)CYCLOALKANONES

Article abstract of DOI:10.1016/S0040-4039(01)90381-8

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 unusual large chemical shift for this type of proton.