Catalytic Enantioselective Access to Dihydroquinoxalinones via Formal α‐Halo Acyl Halide Synthon in One Pot

An enantioselective one-pot catalytic strategy to dihydroquinoxalinones,featuring novel 1-phenylsulfonyl-1-cyano enantioenriched epoxides as masked a-halo acyl halide synthons,followed by adomino ring-opening cyclization (DROC),isdocumented. Apopular quinine-derived urea served as the catalyst in two out of the three steps performed in the same solvent using commercially available aldehydes,(phenylsulfonyl)acetonitrile,cumyl hydroperoxide and 1,2-phenylendiamines.Medicinally relevant 3-aryl/alkyl-substitut-ed heterocycles are isolated in generally good to high overall yield and high enantioselectivity (up to 99î). Arare example of excellent reusability of an organocatalyst at higher scale,subjected to oxidative conditions,isdemonstrated. Mechanistically,labile a-ketosulfone has been detected as the intermediate involved in the DROC process.Theoretical calculations on the key epoxidation step rationalizethe observed stereocontrol, highlighting the important role played by the sulfone group.