Shapiro reaction

The Shapiro reaction is a chemical reaction, which is used in the synthesis of olefins from ketones using a Arylsulfonhydrazids. The base case used lithium alkyls. In addition, the Shapiro reaction enables the synthesis of lithiated alkenes. The Shapiro reaction is mechanistically closely related to the Bamford - Stevens reaction. The reaction is named after its developer Robert H. Shapiro.

Mechanism

First condenses Arylsulfonhydrazid to the ketone. This is then deprotonated by two molecules of lithium alkyl ( for example methyl or butyllithium ). The resulting dianion then stabilizes with elimination of the Arylsulfinats. The cleavage of molecular nitrogen leads to the formation of the lithiated alkene. With aqueous workup of the reaction solution to this is protonated to form an alkene.

If the reaction mixture is not subjected to aqueous, the lithiated alkene also be used as nucleophile. This allows, for example, the coupling of the alkene to a metal center, for example for the production of cuprates. Also it can ( for example, halogen alkanes) are alkylated at this position by adding electrophiles.