Treatment of a wide variety of 2-(2-arylhydrazino) tropones with ethanolic acid at 50–80° C readily gave the benzidine type rearrangement products, ie 2-amino-5-(4-aminoaryl) tropones, which in turn were conveniently led to the corresponding 5-aryltropolones that can be utilized for synthesizing B-ring-open analogues of colchicine.
[Nozoe, Tetsuo; Takase, Kahei; Yasunami, Masafumi; Ando, Masayoshi; Saito, Hiroaki; et al. Bulletin of the Chemical Society of Japan, 1989 , vol. 62, # 1 p. 128 - 142]
