Synthesis of 2H-Thiopirano[3,4-c]pyrazol-7-one Derivatives as the First Example a New Heterocyclic System.

A series of ethyl 4-[(Z)-(4-oxo-2-thioxo-1,3-thiazolidin-5-ylidene)methyl]-1-aryl-1H-pyrazole-3-carboxylates was obtained as a result of the reaction of ethyl 4-formyl-1-aryl-1H-pyrazole-3-carboxylates with rhodanine. Under the action of NaOH, the prepared pyrazole-3-carboxylates underwent recyclization to form 2-aryl-7-oxo-2,7-dihydrothiopyrano[3,4-c]pyrazole-5-carboxylic acids—the first representatives of new heterocyclic system. [ABSTRACT FROM AUTHOR]