Stereoselective Synthesis of All-Carbon Tetrasubstituted Alkenes

Key words

lithium - magnesium - palladium - tetrasubstituted alkenes

Significance

The stereoselective synthesis of various all-carbon tetrasubstituted alkenes is disclosed, employing a two-step protocol which includes the stereoselective generation of an alkenyl pseudohalide followed by stereospecific palladium-catalyzed cross-coupling. The appropriate tetrasubstituted alkenes are obtained in good yield and with good diastereomeric ratios, providing mainly the Z-isomers.

Comment

The reaction is proposed to proceed via a ketene intermediate which is stereospecifically attacked by a lithium organyl to form the trisubstituted enolate moiety attached to a pseudo-halide group [OTf or OP(P)(OR)₂]. This moiety may be converted into other functional groups by palladium-catalyzed cross-couplings to give the corresponding all-carbon tetrasubstituted alkenes.