2-HETERO SUBSTITUTED SILYLATED KETENE ACETALS - REAGENTS FOR THE PREPARATION OF ALPHA-FUNCTIONALIZED METHYL KETONES FROM CARBOXYLIC-ACID CHLORIDES

Silylated ketene acetals of structure XCH=C(OR)OSi(CH3)3 (X = OCH3, OSi(CH3)3, OC6H5, or SCH3; R = CH3 or Si(CH3)3) have been prepared by silylation of appropriate ester enolates. The reaction of a carboxylic acid chloride (R'COCl) with 2 equiv of these reagents either under thermal or Lewis acid catalytic conditions followed by hydrolysis-decarboxylation of intermediates R'(OSi(CH3)3)C=C(X)CO2R gives α-functionalized methyl ketones (R'COCH2X) in preparatively useful yields. Factors which would influence the choice of proper reaction conditions are discussed. © 1979, American Chemical Society. All rights reserved.