Theoretical study of the bifunctional-urea catalyzed Michael reaction of 1,3-dicarbonyl compounds and nitroolefins: reaction mechanism and enantioselectivity

The Michael reaction of nitroalkenes catalyzed by a bifunctional-urea is studied using density functional theory (DFT) calculations, to determine the detailed catalytic mechanism and key factors controlling the enantioselectivity. Four reaction channels, corresponding to the different approach modes of nitroalkenes to a chiral scaffold and different processes of second proton transfer, have been characterized. The rate determining step is proton transfer from the amino group of a catalyst to an α-carbon of nitronate, and the enantioselectivity is controlled by the steps involved in carbon–carbon bond formation. The calculated results provide a general model that explains the mechanism and enantioselectivity of the title reaction.

Graphical abstractThe rate determining step of the Michael reaction of nitroalkenes catalyzed by bifunctional-urea is found to be proton transfer from the amino group of the catalyst to the α-carbon of the nitronate, and the enantioselectivity is controlled by the steps involved in carbon–carbon bond formation.Figure optionsDownload full-size imageDownload as PowerPoint slide