Brønsted base-catalyzed assembly of sulfochromeno[4,3-b]pyrrolidines via tandem [3 + 2] cycloaddition–SuFEx click reaction of ethenesulfonyl fluorides and o-hydroxyaryl azomethines

Abstract

The synthesis of sulfochromeno[4,3-b]pyrrolidines is described. Under the catalysis of a 20 mol% Brønsted base and using molecular sieves 4 Å as an HF scavenger, o-hydroxyaryl azomethines react with ethenesulfonyl fluorides through a tandem [3 + 2] cyclization–SuFEx click reaction to produce sulfochromeno[4,3-b]pyrrolidines in high yields. A reasonable reaction mechanism was proposed based on ¹⁹F NMR experiments and DFT calculations.