Alkyne-coupling reactions catalyzed by OsHCl(CO)(PiPr3)2 in the presence of diethylamine

Abstract

Complex OsHCl(CO)(PiPr3)2, in the presence of diethylamine, catalyzes the dimerization of terminal alkynes HC≡CR (R = Me3C, Cy, Ph, and Me3Si). The reactions initially give butatrienes RCH=C=C=CHR, which are stable under the reaction conditions for R = Me3C and Cy. For R = Ph, the butatrienes polymerize to -[CH(Ph)C≡CCH(Ph)]n-, while for R = Me3Si, the butatriene isomerizes into the enyne Z-Me3SiCH=CH-C≡CSiMe3. The formation of butatrienes takes place via butenynyl intermediates of the type Os(C≡CR){η3C(C≡CR)=CHR}(CO)(Pi Pr3)2.