The Squaramide-Catalyzed 1,3-Dipolar Cycloaddition of Nitroalkenes with N-2,2,2-Trifluoroethylisatin Ketimines: An Approach for the Synthesis of 5′-Trifluoromethyl-spiro[pyrrolidin-3,2′-oxindoles]

A Cinchona alkaloid-derived squaramide-catalyzed asymmetric cycloaddition of trfluoromethyl-containing azomethine ylides with beta-nitroalkenes was realized under mild conditions. A series of biologically important 5'-trifluoromethyl-spiro[pyrrolidin-3,2'-oxindoles] was synthesized efficiently by this process in excellent yields, enantioseletivities and diastereoselectivities.