Hydrophosphination of alkynes and related reactions catalyzed by rare-earth amides

Abstract

Intermolecular hydrophosphination of alkynes with Ph 2PH was effectively catalyzed by Yb-imine complex [Yb(η 2-Ph 2CNPh)(hmpa) 3], in which the empirical rate law was described as v = k [catalyst] 2 [alkyne] 1 [phosphine] 0. The active catalysts were proved to be ytterbium(II) mono- and diphosphido species generated in situ. Although trivalent phosphido complex [Yb(PPh 2) 3(hmpa) n ], gave the same results as the divalent complexes, Yb metals of the both complexes seemed to keep their original oxidation state unchanged. When Ph 2PH was substituted by Ph 2P–SiMe 3, silylphosphination of aromatic internal alkynes took place to afford 1-trimethylsilyl-2-diphenylphosphinoalkenes in moderate yields. Moreover, one-pot synthesis of 1-diphenylphosphino-1,3-butadienes from terminal alkynes and Ph 2PH has been achieved using Y[N(SiMe 3) 2] 3 catalyst through the alkyne dimerization and subsequent hydrophosphination.