146 Synthetic Routes to AromaticC-Nitro Compounds
CH 3NH 2
36NO 2O 2 N
NHNO 2
37O 2 NCH 3
NO 2CH 3NH 2
38O 2 NNO 2NO 290 % HNO 3 ,
AcOH, Ac 2 O90 %H 2 SO 4 , 0 °C88 %Figure 4.16Chemists 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 2NO 2
NO 2
39NHNO 2NO 2
NO 2
40NO 2
41NO 2NO 2NH 2NO 2
NO 2
42O 2 NNH 2+HNO 3 , Ac 2 O76 %H 2 SO 441 : 42 ~ 40:6074 %Figure 4.17The 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 2NO 2
43
(DINOL)O 2 NFigure 4.18Reaction 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