A Rhodium-Mediated, Sfepwise Trimerization of an Alkyne That Docs Not Lead to a Bcnzene hut Selectively to a Hevadienyne Derivative

摘要

Since the pioneering work by Reppe et al. it is well known that varous transition metal compounds catalyze the cyclolrimcr-ization of alkynes to henzene derivatives. With regard to the mechanism of the reaction, it is generally assumed that initiallytwo alkyne molecules coordnate to the metal atom, that in the next step by oxidative coupling the formation of a metailacy-clopentadiene occurs, and that finally this reactive intermediate reacts with another alkyne to give the cyclic trinur. Vollhardt in particular has transformed the [2 + 2 + 21 cvcioaodition of aikynes or of alkynes and olefins mediated by cyclopentadieiv. 1-cobalt compounds into a useful and widespread synthetic methodology.