1994 Volume 52 Issue 6 Pages 521-529
Three types of new heteroatom-stabilized carbanion equivalents have been developed : an α-keto vinyl anion equivalent (A), a vinyl anion equivalent (B), and an acetylide equivalent (C). These equivalents have a seleno, thio or sulfinyl group and a stannyl or silyl group at the α and β positions of the carbanion center, respectively, which work together as an olefin masking group. The equivalent A leads to a convenient synthesis of 2-alkyl-2-cycloalken-l-ones as well as an extremely shortstep-synthesis of the prostaglandin enone key intermediate. The procedure is composed of three consecutive reactions, starting with 2-seleno (thio) -2-cycloal-ken-1-ones, (i) conjugate addition of stannyl- or silyl-lithium, alkylation, and (iii) destannyl (silyl) -selenenylation. Optically, active allylic and propargylic alcohols can be efficiently prepared by the reaction of aldehydes with equivalents B and C derived from chiral β-silylethyl sulfoxides and β-silylvinyl sulfoxides, respectively.
