A DFT study on hetero-Diels-Alder reactions catalyzed by cobalt complexes: Lewis acidity enhancement as a consequence of spin transition caused by Lewis base coordination

(Chemical Equation Presented) Density functional calculations on the hetero-Diels-Alder reaction catalyzed by 3-oxobutylideneaminatocobalt(II) and -cobalt(III) complexes revealed that axial coordination of an aldehyde as a Lewis base induces a spin transition in the Co^III catalytic cycle. The Lewis acidity of the complex is increased, the Co-O_aldehyde distance shortened (see picture; Co green, N blue, O red), and the enantioselectivity improved.