Gabbutt, C. D., Hepworth, J. D., Heron, B. M., Coles, S. J. and Hursthouse, M. B.
Synthesis of some thiochromeno 4,3-c - and 3,4-c -pyrazoles
Journal of the Chemical Society, Perkin Transactions 1, (17), . (doi:10.1039/b004149l).
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Reaction of 3-hydroxymethylene- and 3-cyanomethylene-thiochroman-4-ones with various hydrazine derivatives affords 4H-thiochromeno[4,3-c]pyrazoles. The novel isomeric thiochromeno[3,4-c]pyrazoles result when 4-(dimethylaminomethylene)thiochroman-3-ones react with methyl- and phenyl-hydrazines. Acidic hydrolysis of 3-(dimethylhydrazonoethylidene)-2,2,6-trimethylthiochroman-4-one yields the 3-cyanomethylenethiochroman-4-one. Formation of 6-chloro-3-hydroxymethylenethiochroman-4-one is accompanied by a thiochroman-3-yl(oxothiochromen-3-yl)methane derivative produced through a rearrangement-carbocation interception sequence. A 3-isopropenylthiochromenone, obtained by the acid promoted rearrangement of a 3-hydroxymethylenethiochroman-4-one, undergoes Diels-Alder cycloadditions to provide a new route to thioxanthenones.
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