Enantioselective synthesis of 2-amino-5,6,7,8-tetrahydro-5-oxo-4H-chromene- 3-carbonitriles using squaramide as the catalyst

The organocatalyzed enantioselective synthesis of a series of chiral 2-amino-5,6,7,8-tetrahydro-5-oxo-4H-chromene-3-carbonitriles was achieved using bifunctional squaramides as the catalysts. The tandem Michael addition-cyclization reaction of cyclohexane-1,3-diones and benzylidenemalononitriles gave the corresponding products in excellent yields (up to 99%) and moderate to good enantioselectivities (up to 83% ee). This investigation provides an efficient and useful process for the synthesis of chiral 2-amino-4H-chromenes.