Bifunctional Squaramide-Catalyzed Asymmetric [3+2] Annluation Reactions of 2-Isothiocyanato-1-indanones with 2-Arylidene-1,3-indanediones

A squaramide-catalyzed asymmetric Michael/cyclization tandem reaction between 2-isothiocyanato-1-indanones and 2-arylidene-1,3-indanediones was developed. Under this strategy, the corresponding chiral bispirocyclic indanone compounds containing two contiguous stereocenters were obtained under mild conditions in moderate to excellent yields (up to 99 %) and enantioselectivities (up to 98 % ee). In addition, further transformation experiments were achieved through the oxidation and methylation reactions of the product, which also confirmed the synthetic practicality of this synthetic strategy.