REACTIONS OF 4-CHLORO-3-FORMYLCOUMARIN WITH ARYLHYDRAZINES

Abstract

The interaction of 3-formyl-4-coumarin with arylhydrazine hydrochlorides in the presence of sodium acetate gave the corresponding 3-arylhydrazonomethyl-4-chlorocoumarin, and with phenylhydrazine, 4-bromo- and 4-chlorophenylhydrazine hydrochlorides in the presence of two equivalents of triethylamine gave either 1-aryl- or 2-aryl[1]benzopyrano[4,3-c]pyrazol-4-ones depending on the reaction conditions. In reactions of 4-chloro-3-formylcoumarin with 2,4-dichloro-, 2,4-difluoro-, 2-hydroycarbonyl-, 4-nitro- and 3,5-di(trifluoromethyl)phenylhydrazine,2-pyridyl- and 2-quinoxalyl-hydrazine in the presence of excess of triethylamine the 2-aryl[1]benzopyrano[4,3-c]-pyrazol-4(2H)-ones were obtained exclusively. The structures of 1-phenyl- and 2-(2-pyridyl)[1]benzopyrano[4,3-c]-pyrazolo-4(1H)ones were confirmed by X-ray crystallography. A simple method is proposed to distinguish between 1- and 2-substituted [1]benzopyrano[4,3-c]pyrazolo-4-ones on the basis of the ¹H NMR chemical shifts of the C(3)-H proton in two solvents – DMSO-d₆ and CDCl₃.

How to Cite
Strakova, I.; Petrova, M.; Belyakov, S.; Strakovs, A. Chem. Heterocycl. Compd. 2003, 39, 1608. [Khim. Geterotsikl. Soedin. 2003, 1827.]

For this article in the English edition, see DOI 10.1023/B:COHC.0000018338.41222.a2