Publications [#234625] of Ross A. Widenhoefer

Journal Articles

  1. Harris, RJ; Nakafuku, K; Widenhoefer, RA, "Kinetics and mechanism of the racemization of aryl allenes catalyzed by cationic gold(I) phosphine complexes.", Chemistry (Weinheim an der Bergstrasse, Germany)September,, 2014, 20(38), 12245-12254 [doi].
    (last updated on 2024/04/24)

    Abstract:
    The kinetics of the racemization of aromatic 1,3-disubstituted allenes catalyzed by gold phosphine complexes has been investigated. The rate of gold-catalyzed allene racemization displayed first-order dependence on allene, and catalyst concentration and kinetic analysis of gold-catalyzed allene racemization as a function of allene and phosphine electron-donor ability established the accumulation of electron density on the phosphine atom and the depletion of electron density on the terminal allenyl carbon atoms in the rate-limiting transition state for racemization. These and other observations were in accord with a mechanism for allene racemization involving rapid and reversible inter- and intramolecular allene exchange followed by turnover-limiting, unimolecular conversion of a chiral gold η(2)-allene complex to an achiral η(1)-allylic cation intermediate through a bent and twisted η(1)-allene transition state. With respect to proper ligand selection, these studies reveal that both electron-poor phosphine ligands and polar solvents facilitate racemization.