Bifunctional Squaramide‐Catalyzed Asymmetric Michael/Cyclization Reactions of 3‐Hydroxychromenones with Isatylidenemalononitriles

Abstract

A squaramide‐catalyzed asymmetric Michael/cyclization tandem reaction between 3‐hydroxychromenones and isatylidenemalononitriles was developed. Using this strategy, a wide scope of spiro[indoline‐3,4′‐pyrano[3,2‐b]chromene] derivatives, which combined chromone, pyran, indolone in one molecule, could be obtained in moderate to excellent yields (up to 94 %) with moderate enantioselectivities (up to 95 % ee). In addition, the scaled‐up experiment also confirmed the synthetic practicality of this synthetic strategy.