Expeditious Assembly of a 2‐Amino‐4<i>H</i>‐chromene Skeleton by Using an Enantioselective Mannich Intramolecular Ring Cyclization–Tautomerization Cascade Sequence

Abstract

Easy to assemble! An enantioselective cascade Mannich intramolecular ring cyclization–tautomerization reaction of malononitrile with 2-hydroxyl N-protected α-amido sulfone is described (see scheme), which provides a new route to the synthesis of the privileged scaffold 2-amino-4H-chromene in high yields (up to 94 %) and with good to high enantiomeric excesses (74–89 % ee).