DFT exploration of mechanistic pathways of an aza-Morita-Baylis-Hillman reaction

A new bimolecular pathway for a model aza-MBH reaction is presented and then explored in more details by DFT/M06-2X calculations. For this bimolecular pathway, explicit formic acid was considered in the rate-determining step showing the beneficial action from this additive, which plays a role as a co-catalyst. According to the current computations, this mechanistic cycle is a feasible pathway for the formation of the aza adduct and it explains the experimental detection of a key intermediate. A comparative analysis of the current results and previous ones reveals the substrate and medium dependence of the aza-MBH reaction. These factors lead to distinct pathways for the reaction, uncovering the complexity for conducting this reaction. (AU)