Cycloadditions of thiocarbonyl ylides with N-sulfinylamines

Thiobenzophenone S-methylide (6) and 2, 2, 4, 4-tetramethyl-3-thioxocyclobu tanone S-methylide (17) were allowed to react with N-sulfinylaniline (7) an d N-sulfinyltosylamide (8) furnishing 1,3,4-dithiazolidine 3-oxides. Howeve r, in the interaction 17 + 8 the main product was the 1,2,4-oxadithiolane 2 -tosylimide (22); that is, the adduct to the S=O bond. An X-ray analysis co nfined structure 22 and revealed an envelope conformation of the heteroring . A tentative interpretation considers a switching from the connerted addit ion to the N=S bond of N-sulfinylamines to a two-step pathway via a zwitter ion leading to 22. (C) 1999 John Wiley & Sons, Inc.