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).