A new preparation of substituted 4H-1-benzothiopyran-4-ones from C(alpha),N-benzoylhydrazones or C(alpha),N-carboalkoxyhydrazones and methyl thiosalicylate

摘要

C(alpha),N-Benzoylhydrazones or C(alpha),N-carboalkoxyhydrazones were dilithiated with excess lithium diisopropylamide, and the dianion-type intermediates were condensed with lithiated methyl thiosalicylate, followed by cyclization/hydrolysis to substituted 4H-1-benzothiopyran-4-ones (thioflavones/thiochromones). [References: 38]