Benzopyrones. Part VIII. Mono- and di-tetrazol-5-ylchromones. The infrared cyano-absorption of some 4-oxochromencarbonitriles

Abstract

Some chromones containing a nitrile group at C-2, C-6, or C-8, or at both C-2 and C-6, have been synthesized, l.r. absorption by a nitrile group at C-6 or C-8 is of normal intensity, but that of such a group at C-2 is over 100 times less intense, and is not visible at the concentrations commonly used. Reasons for this behaviour are suggested and the difference in absorption was used to identify the mononitrile obtained by successive amidification and dehydration of diethyl 4-oxochromen-2,6-dicarboxylate. Ethyl 7-ethoxycarbonylmethoxy-4-oxochromen-2-carboxylate also gave a mononitrile; the structure of the latter was proved by the synthesis of both possible products; neither of the nitrile groups of 7-cyanomethoxy-4-oxochromen-2-carbonitrile absorbs appreciably in the CN stretching region. Most of the 4-oxochromencarbonitriles were converted into the corresponding mono- and di-tetrazoles, some of which show a high level of activity as antiallergic agents. 4-Methyl-3-(tetrazol-5-yl)-coumarin is inactive.