44 Synthetic Routes to AliphaticC-Nitro
Frankel and Klager^289 have reported using the Mannich reaction for the condensation of
2,2-dinitroalkanols with ammonia and hydrazine. This method was used to synthesize 2,2,6,6-
tetranitro-4-azaheptane (100 %) and bis(2,2-dinitropropyl)hydrazine (162) (73 %) from the
reaction of 2,2-dinitropropanol (25) with ammonia and hydrazine hydrate respectively. This
work was later extended to using polynitroaliphatic amines and diamines.^284
FCHC 2 NH 2NO 2NO 2NN NCH 2 CF(NO 2 ) 2(O 2 N) 2 FCCH 2 CH 2 CF(NO 2 ) 2MeOH (aq)
FCHC 2 NH 2NO 2NO 2NO 2
CNO 2CH 2 OHFNO 2
FCHC 2 NHCH 2NO 2CNO 2NO 2F64 %CH 2 O, HCl41 %+Figure 1.77Mannich bases derived from polynitroalkanes are usually unstable because of the facile
reverse reaction leading to stabilized nitronate anions. The nitration of Mannich bases to
nitramines enhances their stability by reducing the electron density on the amine nitrogen
through delocalization with the nitro group. The nitration of Mannich bases has been ex-
ploited for the synthesis of numerous explosives, some containing both C–NO 2 and N–NO 2
functionality.^293 ,^295 ,^297 Three such compounds, (163), (164) and (165), are illustrated below
and others are discussed in Section 6.10.
NO 2CCH 2
NO 2O 2 NNNO 2CH 2NO 2F CCH 2
NO 2NNO 2CH 2 CH 2 ONO 2NO 2
CCH 2NO 2O 2 NNNO 2
CH 2 CNO 2NO 22163 1652164Figure 1.781.10.4 Henry reaction
Polynitroaliphatic alcohols are invaluable intermediates for the synthesis of energetic materials
(see Section 1.11). The most important route toβ-nitroalcohols is via the Henry reaction where
a mixture of the aldehyde and nitroalkane is treated with a catalytic amount of base, or the
nitronate salt of the nitroalkane is used directly, in which case, on reaction completion, the
reaction mixture is acidified with a weak acid. Reactions are reversible and in the presence of
base the salt of the nitroalkane and the free aldehyde are reformed. This reverse reaction is
known as demethylolation if formaldehyde is formed.
HC(NO 2 ) 3 + (CH 2 O)n CCH 2 OHNO 2NO 2O 2 NCCl 4112 65 °C, 80 %159Figure 1.79