Enantioselective synthesis of spiro[indoline-3,4′-pyrano[2,3-c]pyrazole] derivatives via an organocatalytic asymmetric Michael/cyclization cascade reaction

Abstract

An efficient enantioselective synthesis of spiro[indoline-3,4′-pyrano[2,3-c]pyrazole] derivatives by a cascade reaction between pyrazolones and isatylidene malononitriles is described. With only 1 mol% of (DHQD)₂PYR, chiral spirooxindole derivatives have been produced in excellent yields (96–99%) with good-to-excellent enantioselectivities (up to 91% ee).