Preparation and reactions of cis-1,4-diphthaloyltetra-az-2-ene

Abstract

Oxidation of N-aminophthalimide with lead tetra-acetate in the absence of additives gives mainly trans-1,4-diphthaloyltetra-az-2-ene (2), but in the presence of certain sulphur compounds (benzo[b]thiophen, dibenzo[b,d]-thiophen, and diphenyl sulphide) the corresponding cis-tetra-azene (7) is the major product. Unlike the trans-tetra-azene, the cis-compound undergoes thermolysis in boiling benzene to give N-(o-isocyanatobenzoyl)phthalimide (18), which in the presence of phthalimide anion gives 2-phthalimido-3,1-benzoxazin-4-one (25). Reactions of the two tetra-azenes with sodium methoxide are described, together with a possible mechanistic link with the conversion of (7) into (18).