Asymmetric synthesis of spirooxindole-fused spirothiazolones via squaramide-catalysed reaction of 3-chlorooxindoles with 5-alkenylthiazolones

An efficient and practical organocatalyzed asymmetric formal [2 + 1] cycloaddition of 3-chlorooxindoles with 5-alkenyl thiazolones by using hydroquinine-derived squaramide as the catalyst has been developed. Under mild conditions, a broad range of spirooxindole-fused spirothiazolones bearing three adjacent stereogenic centers including two vicinal spiro quaternary chiral centers were obtained in high yields (up to 99% yield) with excellent diastereoselectivities (up to >99 : 1 dr) and enantioselectivities (up to 99% ee).