Peterson Olefination

Peterson Olefination is also known as Peterson reaction or Peterson elimination in which an alkene is formed under acidic or basic condition from a β-hydroxyalkylsilanes which is formed by an α-silyl carbanion and a carbonyl compound. When the α-silyl carbanion contains electron-withdrawing substituents, the Peterson olefination directly forms the alkene. The intermediate β-hydroxysilane cannot be isolated as it eliminates in-situ.

Mechanism of Peterson Olefination

Elimination under acidic condition should proceed via anti- manner while under basic conditions should proceed in a syn manner. Two possible pathways have been postulated for the elimination of a silyloxide moiety after deprotonation of a hydroxy group with an equimolar amount of base. One is the stepwise 1,3-migration of a silyl group from carbon to oxygen, followed by elimination of a trimethylsilyloxide moiety and the other involves the formation of a penta-coordinate 1,2-oxasiletanide and extrusion of the trimethylsilyloxide moiety therefrom.

Stereochemistry of Peterson Olefination

The most important feature of the Peterson reaction is that either geometric isomer of an alkene can be prepared from a common single diastereomer of the β-hydroxyalkylsilane intermediate depending on the conditions (acidic or basic) of the reaction.