Phenanthridines. III. Syntheses of 9-bromophenanthridine and 7-bromophenanthridine by Pschorr reactions with sulphonamides derived from N-p-bromobenzyl- and N-o-bromobenzyl-o-phenylenediamines, and a new route to N-sulphonylcarbazoles

Abstract

9-Bromophenanthridine (Ic) has been prepared by oxidative hydrolysis of 9-bromo-5-p-toluenesulphonyl-j,8-dihydrophenanthridine (IIc), which is one of the products of the copper-catalysed decomposition of diazotized N-p-bromobenzy1.N-p- toluenesulphonyl-o-phenylenediamine (IIIc). 7-Bromophenanthridine (Ie) was similarly synthesized from N-o-bromobenzyl-N-methanesulphonyl-o-phenylenediamine (IIIe) by way of 9-bromo-5-methanesulphonyl-5,6-dihydrophenanthridine (IIe). The decomposition of diazotized o-bromobenzyl-N-p-toluenesulphonyl-o- phenylenediamine (IIId) did not yield the corresponding phenanthridine derivative (IId). By-products formed in the cyclization of (IIIc) include 2-p-bromobenzylamino-4'-methylbiphenyl (Vc), 4-bromo-2'-p-toluenesulphonamidobiphenyl (VIc), and N-p-bromobenzyl-2-amino-5'-methylbiphenyl-2'-sulphonic acid sultam (IVc). The amine (IIId) gave 2-o-bromobenzylamino-4'-methylbiphenyl (Vd), 2-bromo-2'-p-toluenesulphonamidobiphenyl (VId), N-o-bromobenzyl-2-amino-5'-methylbiphenyl- 2'-sulphonic acid sultam (IVd), and AT-p-toluenesulphonylcarbazole (VIIa). The amine (IIIe) gave also 2-bromo-2'-methanesulphonamidobiphenyl (VIe) and N-methanesulphonylcarbazole (VIIb). The relative yields of these products depend inter alia on the amount of sodium nitrite used during the inverse diazotization prior to the addition of copper. Under the influence of cuprous compounds the 2-amino-2'-bromobiphenyls (VId) and (VIe) are converted in high yields to the carbazoles (VIIa) and (VIIb), respectively.