Reductiveringcleavage of thiochromane and benzodihydrothiophene by the radicalanion 4,4′-di-tert-butylbiphenylide (LDBB) leads to organolithium compounds bearing a lithium arylthiolate group. The adducts of the latter with aldehydes and ketones undergo ring closure when treated under appropriate acidic conditions. The result is a two-pot one-carbon subsititutive ring expansion of the original sulfur