A new cinnoline synthesis. Part IV. Nitration and sulphonation of chloro-(5,6,7,8)-4-hydroxy-cinnolines

Abstract

Nitration of chloro-(5,6,7,8)-4-hydroxycinnolines and the corresponding 3-carboxylic acids with nitric acid alone, and with mixed acid, has been studied. The structures of the nitro-compounds formed have been determined chemically and/or by n.m.r. measurements. With nitric acid alone the chloro-4-hydroxycinnolines gave increased amounts of the 3-nitro-derivatives. In general the direction of substitution appears to be dictated by the 1,2-diaza-grouping present in the cinnoline system, and only slightly by the chloro-substituent. Sulphonation of 5- and 8-chloro-4-hydroxycinnolines gave the corresponding 8- and 5-sulphonic acids, respectively, the structures of which were confirmed by n.m.r. studies.