A new generation of 'instant ylids': Powder mixtures of phosphonium salts and potassium hydride as storable precursors to Wittig reagents

Mixing a finely pulverized alkyltriphenylphosphonium salt and potassium hydride in 1:1 molar ratio gives a ready-to-use powder the components of which react rapidly when tert-butyl methyl ether is added under stirring. When, in general after a few minutes, the generation of the (triphenylphosphonio)alkanide is complete, it can be immediately used for the Wittig olefination of a carbonyl compound. Compared to sodium amide based 'instant ylids', the new blends offer little advantage as long as simple phosphonium salts are ingredients but they extend considerably the shelf life of mixtures containing heterosubstituted derivatives such as methylthiomethyl- or picolyltriphenylphosphonium salts. Copyright (C) 1996 Elsevier Science Ltd.