Enantioselective synthesis of spiro[4H-pyran-3,3 '-oxindole] derivatives catalyzed by cinchona alkaloid thioureas: Significant water effects on the enantioselectivity

摘要

An efficient stereoselective three-component reaction for the synthesis of functionalized spiro[4H-pyran-3,3 '-oxindole] derivatives was realized through an organocatalyzed domino Knoevenagel/Michael/cyclization reaction using a cinchonidine-derived thiourea as the catalyst. Using water as the additive was found to improve the product ee values significantly. Under the optimized conditions, the reactions between isatins, malononitrile, and 1,3-dicarbonyl compounds yield the desired spirooxindole products in good yields (71-92%) and moderate to high ee values (up to 87% ee).