Carbonyl and thiocarbonyl compounds. Part XIII. 2-Aroyl-1,3-benzodioxoles of potential pesticidal activity and their cleavage with hydrazines

Abstract

2-Aroyl-4,5,6,7-tetrahalogeno-1,3-benzodioxoles (1) are readily obtained through the uncatalysed interaction between tetrahalogeno-o-benzoquinones and the corresponding α-diazo-acetophenone or -acetonaphthone. They behave differently from all other methylenedioxy-compounds previously investigated with respect to cleavage by nucleophilic reagents. They react with phenylhydrazine in boiling n-butanol affording the corresponding arylglyoxal bisphenylhydrazones (6) in high yields. However, they resist cleavage by benzoylhydrazine, by malononitrile, and by cyanoacetic ester under similar conditions. The reaction mechanism is discussed. The osazones obtained are cyclised readily by copper sulphate in aqueous dioxan, affording the corresponding 4-aryl- 2-phenyl-1,2,3-triazoles (7).