- Transition state analysis of enantioselective Brønsted base catalysis by chiral cyclopropenimines.
Transition state analysis of enantioselective Brønsted base catalysis by chiral cyclopropenimines.
Journal of the American Chemical Society (2014-07-17)
Jeffrey S Bandar, Gregory S Sauer, William D Wulff, Tristan H Lambert, Mathew J Vetticatt
PMID25029194
摘要
Experimental (13)C kinetic isotope effects have been used to interrogate the rate-limiting step of the Michael addition of glycinate imines to benzyl acrylate catalyzed by a chiral 2,3-bis(dicyclohexylamino) cyclopropenimine catalyst. The reaction is found to proceed via rate-limiting carbon-carbon bond formation. The origins of enantioselectivity and a key noncovalent CH···O interaction responsible for transition state organization are identified on the basis of density functional theory calculations and probed using experimental labeling studies. The resulting high-resolution experimental picture of the enantioselectivity-determining transition state is expected to guide new catalyst design and reaction development.
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Sigma-Aldrich
(S)-2-(2,3-Bis(dicyclohexylamino)cyclopropenimine)-3-phenylpropan-1-ol hydrochloride, ≥95%