Wittig gem-difluoroolefination of aldehydes with difluoromethyltriphenylphosphonium bromide

Wittig reaction of aldehydes with difluoromethyltriphenylphosphonium bromide leading to gem-difluoroolefins in moderate yields is described. The reaction displays a good substrate scope including aryl, heteroaryl and α,β-unsaturated aldehydes. Difluoromethyltriphenylphosphonium bromide could be easily prepared and stored for a long time under air atmosphere. The salt exhibits high thermal stability demonstrated by thermogravimetric analysis. Its structure was confirmed by NMR spectroscopy and single crystal X-ray analysis.