The preparation in three steps of
N-benzyl-N-benzenesulphonyl-o-phenylenediamine (Va), of N-benzyl-N-p-toluenesulphonyl-o-phenylenediamine
(Vb), and of N-benzyl-N-methanesulphonyl-o-phenylenediamine (Vc) from
o-nitroaniline is described. The copper-catalysed decomposition of diazonium
salts of each of these amines in acetic acid-sulphuric acid has been examined.
Compound (Va) gave N-benzyl-2-aminobiphenyl (IXa),
5-benzenesulphonyl-5,6-dihydrophenanthridine (VIa), N-
benzyl-2-aminobiphenyl-2'-sulphonic acid sultam (Xa),
N-benzenesulphonyl-2-amino-biphenyl (XIIa), and phenanthridine. Compound (Vb)
gave N-benzyl-2-amino-4'-methylbiphenyl (IXb),
6-p-toluenesulphonyl-5,6-dihydrophenanth (VIb), a compound C20H17NO2S
thought to be N-benzyl-2-amino-5'-methylbiphenyl-2'-sulphonic acid sultam (Xb),
N-benzyl-N-p-toluenesulphonylaniline (XIb), N-p-
toluenesulphonyl-2-aminobiphenyl (XIIb), and phenanthridine.
Compound (Vc) gave
5-methanesulphonyl-5,6-dihydrophenanthri (VIc),
N-benzyl-N-methanesulphonylaniline (XIc), N-methanesulphonyl-2-aminobiphenyl
(XIIc), and phenanthridine. It has been found that the yields of most of these
products depend inter alia on the excess of sodium nitrite present during the
diazotization prior to cyclization. It is suggested that this effect is caused
by changes in the concentration of cuprous ions present during the cyclization.
Heterolytic and homolytic processes may be involved in the formation of the
dihydrophenanthridines and sultams. The formation of the biphenyl derivatives (IX)
and (XII) is postulated to proceed via the spirane intermediates (XIX) or (XX).�The
conversion of the sulphonamides of dihydrophenanthridine (VI) to phenanthridine
in c. 70% yield completes new syntheses of this ring system.