Highly Enantioselective Organocatalytic α-Sulfenylation of Azlactones

The first asymmetric alpha-sulfenylation of azlactones with N-(sulfanyl)succinimides has been developed by using cinchona alkaloid-derived squaramide as a catalyst and 4 angstrom molecular sieves as an additive. The reaction conditions were suitable to 4-alkyl and benzyl-substituted azlactones as well as N-(benzyl/alkyl/arylthio)succinimides, affording adducts with high enantioselectivities (81-94% ee).