A Computational Model for Asymmetric Induction in the Boron-Mediated Aldol Reactions of Methyl Ketones

Anna Bernardi,(a) Cesare Gennari,(a) Jonathan M. Goodman,(b) and Ian Paterson(b)

(a) Dipartimento di Chimica Organica e Industriale, Universita' di Milano, via Venezian 21, 20133 Milano, Italy
(b) University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, England

Abstract: Force fields have been used to analyse and predict stereoselectivity in the aldol reactions of E and Z enol borinates derived from ethyl ketones with aldehydes. The model is now extended to the corresponding boron-mediated aldol reactions of methyl ketones. The correlation between calculation and experiment is good, for achiral substrates and chiral ligands on boron, with the experimentally-observed reversal in stereoselectivity being reproduced. Trends in selectivity with different substrates appear to be calculated correctly.

Scheme 1: The reversal in stereoselectivity between methyl and ethyl ketones

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