Reactions of tethered, tertiary sulfonamides with thermally generated benzynes are reported. Typically, the N-S bonds in the substrates cleave, and saturated heterocycles [tetrahydroquinolines ( n = 2) and indolines ( n = 1)] are formed. The process is accompanied by either sulfonyl transfer or desulfonylation from a zwitterionic intermediate, with the favored pathway being largely dependent upon the size (5- vs 6-membered) of the N-containing ring in the zwitterion.