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

o -Hydroxyaryl azomethine ylides react with ethenesulfonyl fluorides via a tandem [3 + 2] cycloaddition–SuFEx click process to produce sulfochromeno[4,3- b ]pyrrolidines in high yields.