A stepwise mechanism for the uncatalyzed michael addition of acetylacetone to methyl vinyl ketone

摘要

A stepwise mechanism for the uncatalyzed Michael addition of acetylacetone (AcAc) to methyl vinyl ketone (MVK) has been studied by ab initio calculations at the MP2/6-31+G (d, p)// B3LYP/6-31+G (d, p) level of theory. This stepwise mechanism is initiated by a Diels-Alder-type attack of MVK on the double bond of the cis-enol of AcAc followed by cleavage of the cycloadduct and proton transfer leading to the formal Michael adduct. Nature of interaction between AcAc and MVK has been probed using reactivity descriptors defined within the context of conceptual DFT. This stepwise mechanism is found to have a low barrier than the concerted mechanism proposed earlier.