N-Heterocyclic Carbene-Catalyzed Activation of α-Chloroaldehydes: Asymmetric Synthesis of 5-Cyano-Substituted DihydropyranonesFinancial support from the European Research Council (ERC Advanced Grant 320493, ‘DOMINOCAT’) is gratefully acknowledged.
Received: 26 June 2017
Accepted: 26 June 2017
26 July 2017 (eFirst)
An N-heterocyclic carbene (NHC)-catalyzed asymmetric [4+2] annulation of (E)-2-benzoyl-3-phenylacrylonitriles with α-chloroaldehydes has been developed. The protocol leads to 5-cyano-substituted dihydropyranones in good to excellent yields with excellent diastereo- and enantioselectivities (up to 93% yield, >20:1 d.r. and 99% ee).