Synthesis of isoindole-diimine and its derivatives without ammonia gas bubbling

Abstract

Isoindole-diimine, which can be obtained by bubbling ammonia gas into a solution of phthalonitrile derivatives in the presence of Na[Formula: see text] ion, is a final and best precursor for phthalocyanine synthesis. In this study, isoindole-diimine and various derivatives have been prepared without bubbling ammonia gas using in situ generated ammonia that was produced from formamide and a strong alkali such as NaOH and NaNH2. A longer reaction time, higher temperature, and larger amount of formamide were required for phthalonitrile derivatives with electron-donating groups, but this method is recommendable in that an NH3 gas cylinder and concomitant gas regulator, which are not inexpensive, are not required. Attempts were made to interpret the IR and absorption spectra of the resultant diimines. The signals due to imino proton or N-H of diimino compounds were experimentally found to appear at around 8.2[Formula: see text]9.5 ppm in 1H-NMR and ca. 3500–3000 cm[Formula: see text] in IR spectra.