CLXXXIII.—2:2′-Dibromodiphenyl and 2:2′-dichlorodiphenyl

Cyclization reactions of 2,2'-disubstituted biphenyls

“…Treatment of the diazonium solution from 2,2'-diaminobiphenyl with cuprous bromide gives a mixture of benzo[c]cinnoIine, carbazole, and 2,2'-dibromobiphenyl, the first predominant. Reversal of addition gives carbazole predominantly, the dibromide being a minor constituent in both cases (58). These results are at variance with a later report that the dibromide is the major product (79).…”

“…Diazotization of a series of substituted 2,2 '-diaminobiphenyls (LXXXVII) followed by reduction with hypophosphorous acid gives the corresponding benzo [c jcinnolines in poor to fair yields (22). Diazotization in the presence of cuprous bromide gave a mixture of benzo [cjcinnoline, carbazole, and 2,2'dibromobiphenyl (58), although only the latter was reported in a later investigation (79). Benzo [cjcinnoline is also the product when the diazotization is carried out with sodium arsenite (154).…”