Weygand/Hilgetag Preparative Organic Chemistry

532 Formation of carbon-nitrogen bonds
and sodium hydrogen sulfite afford l,2,3,4-tetrahydro-4-(phenylhydrazono)-2naphthalenesulfonic
acid, which is cyclized by acid to benzo[a]carbazole
(85% yield) in analogy to the Fischer indole synthesis; and benzo[c]carbazole
is obtained similarly from 2-naphthol. 1058
The preparation of amines from phenols that are neither activated by
suitable groups (see page 529) nor amenable to the Bucherer reactions requires
higher temperatures (180-300°) and thus in most cases the use of pressure.
Zinc chloride and diamminodichlorozinc 1074 have often proved their worth
as catalysts; calcium chloride, sodium hydrogen sulfate, iron(m) chloride,
and sulfanilic acid have also been used, but less often. Knoevenagel 1045
obtained very good yields in the arylation of aromatic amines by naphthols
when adding catalytic amounts of iodine. It is often useful to use amine hydrochlorides
instead of the free base. Most of the directions for laboratory-scale
work with simple components are to be found in the older literature. 1074 ' 1075
Two more recent examples may be cited: 3-Amino-2-naphthoic aicd, which cannot be
obtained in 70% yield by the Bucherer reaction, has been prepared by heating 3-hydroxy-
2-naphthoic acid with aqueous ammonia and zinc chloride for 36 h in an autoclave at
195° 1076
For the preparation of 2-phenyl-7-quinolinamine (80% yield), 2-phenyl-7-quinolinol (6.6 g)
was heated with calcium chloride ammoniate (25 g) in a sealed tube at 250° for 3 h and then
at 280-290° for a further 7 h. 1077
An amino group can be introduced in place of a phenolic hydroxyl group
in, e.g., alkylphenols 1078 * 1079 or steroids 1078 ' 1080 by various very effective
processes that depend on oxidizing the phenol by lead tetraacetate to a
^.io78,io8o or 0-quinol 1079 acetate and treating this with a carbonyl reagent
such as semicarbazide, 1078 dinitrophenylhydrazine, 1078 ' 1079 or benzylamine;
1080 the nitrogenous carbonyl derivative becomes aromatic again by
ejecting an acetoxyl group and can then be cleaved to the free amine by
reduction 1078 ' 1079 or by hydrolysis. 1080
4. Reaction of ethers and oxonium salts with nitrogen compounds
Substitution of an amino for the alkoxyl group of simple aliphatic ethers
has little preparative importance: the ether linkage must be weakened by a
carbonyl, carboxyl, or nitrile group in the /^-position if the reaction is to
occur under not too drastic conditions. Certain /?-methoxy ketones of type (17)
can be converted into /?-amino ketones below 100°. 1081 Cleavage of the ether
group in activated enol ethers is still easier; for instance, 2-(acetoxymethylene)-
1074 V. Merz and P. Mtiller, Ber. Deut. Chem. Ges., 19, 2901 (1886).
1075 V. Merz and P. Muller, Ber. Deut. Chem. Ges.9 20, 544 (1887); R. Lloyd, Ber. Deut.
Chem. Ges., 20, 1254 (1887); K. Buch, Ber. Deut. Chem. Ges., 17, 2634 (1884).
1076 C. H. F. Allen and A. Bell, Org. Syn., Coll. Vol. Ill, 78 (1955).
1077 W. Borsche and M. Wagner-Roemmich, Ann. Chem., 544, 294 (1940).
1078 E. Hecker, Chem. Ber., 92, 3198 (1959); E. Hecker and E. Walk, Chem. Ber., 93,
2928 (1960).
1079 H. Budzikiewicz, F. Wessely, and O. S. Ibrahim, Monatsh. Chem., 95, 1396 (1964).
1080 A. M. Gold and E. Schwenk, /. Amer. Chem. Soc, 81, 2198 (1959).
1081 1. N. Nazarow and S. A. Vartanyan, Zh. Obshch. Khim., 22, 1668, 1794 (1952);
Chem. Abstr., 47, 9968, 9969 (1953).