Synthesis of 1,2‐disubstituted naphth [1,2‐d]imidazole‐4,5‐diones

Abstract

A convenient synthesis of 3‐acylamino‐1,2‐naphthoquinones (I) is presented. The addition of aromatic and aliphatic amines to I followed by exposure to oxygen gives the corresponding 4‐arylamino‐ or 4‐alkylamino‐3‐acylamino‐1,2‐naphthoquinones (II). The addition of 4‐cyclo‐hexylbutylamine to 3‐trichloroacetamino‐1,2‐naphthoquinone took an anomalous course and 1‐(4′‐cyclohexylbutyl)‐3(H)‐naphth[1,2‐d]imidazoline‐2,4,5‐trione (VII) was obtained. Treatment of II with refluxing acetic acid gave 1,2‐disubstituted naphth[1,2‐d]imidazole‐4,5‐diones (III). The reaction was successful with a variety of 4‐substituted amino‐3‐acylamino‐1,2‐naphthoquinones (II) and usually occurred in excellent yield. However, the cyclization of II to III is subject to steric limitation and attempts to cyclize 4‐tert‐butylamino‐3‐acetamino‐1,2‐naphthoquinone to the corresponding imidazole derivative was unsuccessful. The infrared, ultraviolet and nuclear magnetic resonance spectra of I, II, and III are discussed in relation to their structures.