146 Synthetic Routes to AromaticC-Nitro Compounds
CH 3
NH 2
36
NO 2
O 2 N
NHNO 2
37
O 2 N
CH 3
NO 2
CH 3
NH 2
38
O 2 NNO 2
NO 2
90 % HNO 3 ,
AcOH, Ac 2 O
90 %
H 2 SO 4 , 0 °C
88 %
Figure 4.16
Chemists at the Naval Air Warfare Center (NAWC), Weapons Division, China Lake, have
reported many examples of polynitroarylamine synthesis via Bamberger rearrangements of
arylnitramines.^139 ,^142 −^145 The nitration of 4-amino-2,5-dinitrotoluene (36) with a mixture of
nitric acid and acetic anhydride in glacial acetic acid at room temperature yields the nitramine
(37) which on treatment with neat sulfuric acid, provides 4-amino-2,3,5-trinitrotoluene (38) as
the sole product.^145 Nitration of 3,4-dinitroaniline (39) with a solution of nitric acid in acetic
anhydride yieldsN,3,4-trinitroaniline (40); acid-catalyzed rearrangement of the latter in neat
sulfuric acid furnishes a 74 % yield of isomeric 2,3,4- (41) and 2,4,5- (42) trinitroanilines in
a 4:6 ratio.^139 Accordingly, a mixture of products can be expected when an unsymmetrical
arylnitramine has two unsubstitutedorthopositions available.
NH 2
NO 2
NO 2
39
NHNO 2
NO 2
NO 2
40
NO 2
41
NO 2
NO 2
NH 2
NO 2
NO 2
42
O 2 N
NH 2
+
HNO 3 , Ac 2 O
76 %
H 2 SO 4
41 : 42 ~ 40:60
74 %
Figure 4.17
The rearrangement of arylnitramines is a synthetically useful reaction. However, on nu-
merous occasions the formation of nitramines during the nitration of anilines can complicate
a reaction. One such problem is the formation of zwitterionic diazo oxides, also known as
diazophenols or diazonium phenolates. These can be formed from nitramines containing a pre-
existingo-nitro group in a process resulting in formal loss of nitric acid. Many diazophenols
are primary explosives and can contaminate products formed from the Bamberger rearrange-
ment of nitramines; DINOL (2-diazo-4,6-dinitrophenol) (43) is a diazophenol and a primary
explosive used in detonators.
O
N 2
NO 2
43
(DINOL)
O 2 N
Figure 4.18
Reaction mixtures containing an arylnitramine with ano-nitro group require careful work-up
because the formation of diazophenols is often a facile and sometimes spontaneous process. The