Organocatalytic Enantioselective Synthesis of Dihydropyrano‐ indole Derivatives Bearing Trifluoromethylated All‐Carbon‐ Substituted Stereocenters

Malononitrile and isatin‐derived trifluoromethylacrylates underwent a Michael addition/cyclization reaction, a process that was catalyzed efficiently by a bifunctional squaramide to afford a range of dihydropyranoindole derivatives bearing trifluoromethylated all‐carbon‐substituted stereocenters in high yields (up to 99%) with excellent enantioselectivity (up to 98% ee). This transformation was also examined with ethyl cyanoacetate as a nucleophile using a bifunctional thiourea as catalyst affording moderate yields (up to 79%) and high enantioselectivity (up to 98% ee). One of the products has been used for the synthesis of a biologically interesting triazolopyrimidine derivative.