Although the reaction of dienolate (1) with aldehydes is frequently lacking in regio- and diastereo-selectivity, the γ-tin substituted derivatives (5), easily obtainable from (1), give (3) and (4) diastereoselectively by controlling the reaction conditions.
Trapping of the lithium dienolate (1), derived from 3-methyl-2-butenoate, with Me3GeX (X = Br or Cl) gives the α-germylated derivative (2), which reacts with various electrophiles at the γ-position.
Stabilization and activation of dienolates with germanium and tin. Stereo- and regioselective aldol reactions, regioselective coupling reactions, and regioselective synthesis of amino acid derivatives