Ytterbium-catalyzed dual intermolecular hydrophosphination: synthesis of bis(phosphinyl)dienes and bis(alkenyl)phosphine oxides

Dual intermolecular hydrophosphination of conjugated diynes with 2 equiv of diphenylphosphine was catalyzed by ytterbium complexes, Yb(η²-Ph₂CNPh)(hmpa)₃ (1) and YbN(SiMe₃)₂]₃(hmpa)₂ (2), to give the corresponding 1,4-bis(diphenylphosphinyl)buta-1,3-dienes in high yields after oxidative work-up. Distribution of the four possible stereoisomers sharply depended on substituents of the substrates. (Z,Z)-Isomers were predominantly obtained from the disubstituted diynes, together with minor (Z,E)-isomers. On the other hand, the reaction of the terminal diynes provided major (E,Z) and minor (E,E)-butadienes. 1,4-Di-tert-butylbuta-1,3-diyne was exclusively converted to an allenic compound. Moreover, the dual hydrophosphination using phenyphosphine was also performed with 1 and 2. Thus, the reaction of 2 equiv of aromatic alkynes with PhPH₂ and subsequent oxidation gave bis(alkenyl)phosphine oxides in preference of the (Z,Z)-stereoisomers.