Organic Reactions Volume 4 - Sciencemadness Dot Org

194 ORGANIC REACTIONS
for example, gave ^-bromodimethylaniline in 88% yield. Aromatic
primary amines without substituents in the reactive oriho and para
positions are converted to resins by treatment with formaldehyde in
acid solution.
Br tfr
Br / \NH2 + 2CH2O + 8(H) -» Br/ \N(CH3)2 + 2HBr + 2H2O
~~Br
p-Aminobenzoic acid has been converted to the tertiary amine by
methylation with formaldehyde, hydrogen, and a catalyst (platinum,
nickel, or cobalt), but the yields are not reported. 77
Aromatic nitro compounds can be converted to dialkylarylamines in
yields of 34-70% by reductive alkylation in the presence of acetic acid
with hydrogen, platinum catalyst, and aliphatic aldehydes other than
formaldehyde. 2 If the nitro compound carries a methyl, methoxyl,
hydroxyl, or amino group in the para position, the use of acetic acid is
unnecessary (see p. 187). 43,44,45 The convenience of this method of preparing
tertiary amines directly from nitro compounds is illustrated by
the comparison of various preparations of di-n-butylaniline shown in
Table VI, p. 206.
The formation of tertiary amines by reductive alkylation of azo
compounds formed by coupling has been mentioned (p. 187) . 48
Benzaldehyde has been used as the alkylating agent in the preparation
of tertiary amines from p-nitrophenol and p-nitroaniline. Both
reactions were carried out over platinum catalyst. The tertiary amine
was isolated in unspecified yield from the nitrophenol; 52 - 63 ' 54 both nitrogen
atoms of the nitro amine were alkylated, tetrabenzyl-p-phenylenediamine
being obtained in 50% yield. 44 These appear to be the only
examples of the use of an aromatic aldehyde as the alkylating agent in
the preparation of tertiary amines from aromatic nitro compounds, and
no similar preparations from primary aromatic amines or azo compounds
are recorded.
From Secondary Aliphatic Amines and Aldehydes and Ketones.
Many secondary aliphatic amines have been alkylated with aliphatic
aldehydes. The yields of tertiary amines obtained have varied from
almost zero to as high as 100%. The highest yields are obtained when
formaldehyde is the alkylating agent (with hydrogen and platinum
catalyst) and when the alkyl groups attached to the nitrogen atom of
the secondary amine are primary or when they form a pyrrolidine or
piperidine ring system. Nevertheless, good yields are obtained in
77 Skita and Stuhmer, Ger. pat. 716,668 [C. An 38, 2345 (1944)].