Enantioselective formation of substituted 3,4-dihydrocoumarins by a multicatalytic one-pot process.

The formation of optically active 3,4-dihydrocoumarins is presented by merging aminocatalysis with an N-heterocyclic carbene-catalyzed internal redox reaction. The products are formed in good to excellent yields and in general with excellent enantioselectivities. Moreover, the developed procedure demonstrates the potential of enantioselective, multicatalytic sequences. By employing an enantiopure aminocatalyst in the enantiodifferentiating step, the challenges related to achieving high stereoinductions by deployment of optically active NHC-catalysts can be circumvented.