Reinvestigation of a 5H‐dibenzo[d,h][1,3,6]triazonine synthesis

Abstract

AbstractTreatment of 5‐chloro‐2‐aminobenzophenone (1) witho‐phenylenediamine, sodium acetate, and acetic acid gave 2‐(acetyl)amino‐5‐chlorobenzophenone (5) rather thanN‐[(2‐amino‐5‐chlorophenyl)phenylmethylene]‐1,2‐benzenediamine (3), as reported by Kulkarniet al, [1]. Authentic3was prepared and treated with chloroacetic acid and polyphosphoric acid (PPA) to give1, recovered3, 2,8‐dichloro‐6,12‐diphenyldibenzo[b,f][1,5]diazocine (9) and 2‐chloro‐6‐(chloromethyl)‐13‐phenyl‐5H‐dibenzo[d,h][1,3,6]triazonine (10). Treatment of5with PPA, with or without chloroacetic acid, gave [5‐chloro‐2‐[(6‐chloro‐4‐phenyl‐2‐quinolinyl)amino]phenyl]phenylmethanone (11) as the sole product in 90% yield. Treatment of other benzophenones, acetophenones, and anilines with sodium acetate and acetic acid provided acetanilides in 78‐96% yield, with the exception of 2′‐aminoacetophenone (20), which gave a quantitative yield of 2‐[((2‐acetyl)phenyl)amino]‐4‐methylquinoline (21). The mechanism of acetanilide formation with sodium acetate and acetic acid is discussed. The structure of21was established using high resolution1H nmr techniques. Attempts to prepare an authentic sample of21from 2‐chlorolepidine (26) and (20) gave 4‐methyl‐N‐[2‐(4‐methyl‐2‐quinolinyl)phenyl]‐2‐quinolinamine (29) as the major product.