Synthesis and Some Transformations of 7-(Fur-2-yl)-1-methyl-1H-pyrazolo[4,3-g][1,3]benzothiazole

Abstract

N-Methylation of 5-nitro-1H-indazole in a KOH–DMSO system resulted in a mixture of 1-methyl-5(6)-nitroindazoles in a ratio of 1: 2. Reduction of the isomers with tin in concentrated hydrochloric acid afforded pure 1-methyl-1H-indazole-6-amine. Condensation of the latter with furoyl chloride in 2-propanol yielded N-(1-methylindazol-6-yl)furan-2-carboxamide, treatment of which with an excess of P2S5 in anhydrous pyridine gave the corresponding carbothioamide. 7-(Fur-2-yl)-1-methyl-1H-pyrazolo[4,3-g][1,3]benzothiazole was synthesized by Jacobson oxidation of N-(1-methylindazol-6-yl) furan-2-carbothioamide with potassium ferricyanide in an alkaline medium. Some transformations of 7-(fur-2-yl)-1-methyl-1H-pyrazolo[4,3-g][1,3]- benzothiazole such as formylation and acylation were performed.