SYNTHESIS OF ASYMMETRIC SECONDARY PHOSPHINES BY THE CROSS COUPLING OF ARYL HALIDES WITH SILYLPHOSPHINES

The cross coupling of aryl halides with alkyl(trimethylsilyl)phosphines catalyzed by zero-valent palladium complexes yields secondary alkylarylphosphoranes containing both electron-donor and electron-withdrawing substituents in the aromatic ring. The reversible disproportionation of alkylsilylphosphines to give AlkPH2 and AlkP(SiMe3)2 was observed for the first time during this reaction. This disproportionation does not affect the yield of AlkArPH, which are formed in virtually quantitative yield, due to the high rate of cross coupling with AlkP(SiMe3)H2 and the reversibility of the disproportionation process.