Paddon-Row, Michael; Kwan, Laurence; Willis, Anthony; Sherburn, Michael
(Chemical Equation Presented) All cis-tems go! The first detailed computational investigations into the title reaction validate Corey's two pre-transition-state models and reveal a third Lewis acid coordination mode (see picture), which operates for esters having s-cis C=C-C=O groups. The new pre-transition-state model explains the unexpected enantioselectivity witnessed for several Diels-Alder reactions and does not involve a C-H⋯O hydrogen bond.
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