Mechanism and origin of enantioselectivity in the Rh2(OAc)(DPTI)3-catalyzed cyclopropenation of alkynes. Academic Article uri icon

abstract

  • The mechanism of cyclopropenations of alkynes with ethyl diazoacetate catalyzed by Rh2(OAc)4 and Rh2(OAc)(DPTI)3 (1) is studied by a combination of kinetic isotope effects and theoretical calculations. With each catalyst, a significant normal 13C KIE was observed for the terminal acetylenic carbon, while a very small 13C KIE was observed at the internal acetylenic carbon. These isotope effects are predicted well from canonical variational transition structures for cyclopropenations with intact tetrabridged rhodium carbenoids. A viable mechanism based on the recently proposed importance of a [2 + 2] cycloaddition on a tribridged rhodium carbenoid could not be identified. An explanation for the enantioselectivity with DPTI ligands is described.

author list (cited authors)

  • Nowlan, D. T., & Singleton, D. A

complete list of authors

  • Nowlan, Daniel T||Singleton, Daniel A

publication date

  • January 1, 2005 11:11 AM