[Reactions between 1,2-naphthoquinones and arylhydrazines]

1,2-Naphthoquinone (8) reacts with arylhydrazines 2 in acetic solution to give 1,2-naphthoquinone-2-arylhydrazones 13 and 2-arylazo-1-naphtholes, respectively. 4-Arylhydrazino-1,2-naphthoquinones 11 are not obtained. On the other hand 8 reacts with the same arylhydrazones 2 in neutral methanolic solution to give 11 and 13. The formation of 13 is remarkable, because 1,4-naphthoquinone (1) does not react with arylhydrazones 2 in neutral methanolic solution to give 6 and because arylhydrazones usually are condensed in acidic solution.