Density functional methods are used to model key steps of the tandem aza-Cope � Mannich reaction leading to a substituted acylpyrrolidine using borontrifluoride as the acid catalyst. The effect of a substituent at the vinylic positionof the iminium cation intermediate is considered with respect to optimizingstereoselectivity in the pyrrolidine reaction product. Activation barriers for the aza-Cope rearrangement and for a series of C-C bond rotations that interconvertstereoisomers are calculated at the M062X/cc-pVQZ level of theory for each ofthe four possible iminium cation stereoisomers and compared to those of theunsubstituted pyrrolidine. We consider the effects of the substituent on the relativestability of the iminium cation intermediate stereoisomers, on the activation energyfor rearrangement and on the activation barriers to interconversion through C-Cbond rotation.

Effect of a bulky substituent on the stereoselectivity of a reaction leading to acylpyrrolidines

248th National Meeting (2014)

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