Preparation of N-aryl-4-oxo-4H-1-benzothiopyran-2-acetamides from trilithiated acetoacetanilides and lithiated methyl thiosalicylate

Acetoacetanilide and substituted acetoacetanilides were trilithiated in excess lithium diisopropylamide, and the polylithiated intermediates were regioselectively condensed with lithiated methyl thiosalicylate, followed by acid cyclization to afford substituted N-aryl-4-oxo-4H-1-benzothiopyran-2-acetamides (thiochromone-2-acetamides).Key words: thiochromones, strong-base multiple anion synthesis, Claisen-type condensation.