The reactivity of primary phosphine-boranes RPH2· BH3 (R= Ph and Me) towards CH2 CHCO2Me and CH2 CHP (O)(OMe) 2 is discussed. Hydrophosphination is the major process. The presence of the free phosphine (0–20%) in the crude media indicates that a competitive hydroboration reaction also occurs. The P H addition was found to be controllable to give, in reasonable yields, either the mono or the bis-adducts. All the ...