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360 Dinitrogen Pentoxide – An Eco-Friendly Nitrating Agent
9.9 Ring cleavage nitration
Chemists at DERA in the UK have reported some of the most important routes to nitramines and
nitrate esters to appear in the past decade. This work involves the use of dinitrogen pentoxide
in chlorinated solvents for the ring cleavage of strained ring nitrogen and oxygen heterocycles.
Reactions proceed under nonacidic conditions and are incredibly efficient, incorporating all
the dinitrogen pentoxide into the product.
O
O
O 2 NO
ONO 2
ONO 2
40
ONO 2
O
HO
O 2 NO ONO 2
ONO 2
38
39
4.0 hr, 73 %
37
N 2 O 5 (> 2 eq), AlCl 3 ,
CH 2 Cl 2 , 0–10 °C
N 2 O 5 (> 2 eq), AlCl 3 ,
CH 2 Cl 2 , 0–10 °C
4.5 hr, 55 %
Figure 9.18
N 2 O 5 (> 2 eq)
CH 2 Cl 2 , 10 °C, 28 h,
88 %
O
41
3 C CH 2 OHH
3 C CH
CH 2 ONO 2
CH 2 ONO 2
42
CH 2 ONO 2
Figure 9.19
Dinitrogen pentoxide in chlorinated solvents reacts with epoxides^65 ,^66 and oxetanes^66 ,^67
to yield 1,2-dinitrate and 1,3-dinitrate esters respectively. Reactions are notably clean and
frequently high yielding for many substrates. Some epoxides containing Lewis basic oxygen
functionality next to the epoxide ring react slowly and so aluminium chloride is added. The route
is general and has been used to synthesize energetic nitrate ester plasticizers like nitroglycerine
(NG) (38) and metriol trinitrate (MTN) (42) and high explosives like erythritol tetranitrate (40).
The latter is not a practical explosive because the starting material, erythritol, is derived from
scarce natural resources i.e. some types of seaweed. The scarcity of other polyols makes this
route all the more attractive for the synthesis of their nitrate esters.
HO
ONO 2
ONO 2
OH
m n−m
44
(NHTPB)
HO
OH
n
43
- CH 3 CO 3 H, CH 2 Cl 2
2. N 2 O 5 , CH 2 Cl 2
Figure 9.20
The synthesis of nitrated hydroxy-terminated polybutadiene (NHTPB) (44) from the re-
action of partially epoxidized hydroxy-terminated polybutadiene with dinitrogen pentoxide
