ChemInform Abstract: An Efficient Procedure for the Synthesis of Pyrazolo(3,4-d)(1,3) thiazin-4-ones

Trichloromethyl chloroformate reacts with N-(1-alkyl/aryl-5-pyrazolyl) thiocarboxamides (2a-j) to give pyrazolo[3,4-d][1,3]thiazin-4-ones (3) while it reacts with N-(3-methyl-5-pyrazolyl)thiobenzamide (2m) to give the pyrazolo[1,5-c] [1,3,5]thiadiazine-4-one (4). Heating under reflux in formic acid of homologues (3g-i) bearing a tert-butyl group linked to pyrazole N-1 atom afforded the dealkylated derivatives (3k-m)