Phosphorous ylides with ketones

The Wittig reaction converts a ketone to an alkene. A phosphorous ylide (pronounced "ill -id") is used. An ylide is a neutral molecule with a negatively charged carbanion. 

The reaction of aldehydes or ketones with phosphorus ylides produces alkenes of unambiguous double-bond locations. Phosphorous ylides are prepared by reacting a phosphine with an alkyl halide, followed by treatment with a base. Ylides have positive and negative charges on adjacent atoms. 

Recently, Xu et al. describled a highly enantioselective Mannich-type three-component reaction of diazoacetophenones 315, alcohols 311, and imines 148 under the cocatalysis of Rh COAc) and phosphoric acid 5 m (Scheme 2.86). In the presence of RhjCOAc), diazoacetophenones and alcohols formed oxonium ylides to serve as the enol equivalents of a-alkoxyl aryl ketones, which then underwent Mannich-type reaction with phosphoric acid-activated imines to produce enantioenriched p-amino-a-hydroxyl ketone products 316 [119],... 

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