Organic Chemistry of Explosives

Nitrate esters from strained oxygen heterocycles 99

of nitrate esters from carbohydrates. In these reactions the intermediate triflate ester is formed

in situand reacted directly with tetrabutylammonium nitrate without prior isolation.

3.3.4 Displacements with mercury (I) nitrate

RBr + HgNO 3 RONO 2 + HgBr (Eq. 3.9)

DME

Figure 3.19

McKillop and Ford^73 synthesized a range of primary and secondary alkyl nitrates in excellent

yields by treating alkyl bromides with mercury (I) nitrate in 1,2-dimethoxyethane at reflux

(Equation 3.9). This method has been used to synthesize substituted nitrate esters from both

α-bromocarboxylic acid andα-bromoketone substrates. Unlike metathesis with silver salts,

which are widely known to promote SN1 reactions, this method is not useful for the synthesis

of nitrate esters from tertiary alkyl halides.

3.4 Nitrate esters from the ring-opening of strained oxygen heterocycles

The strained rings of epoxides and oxetanes are susceptible to nucleophilic attack. In this

section we discuss the reactions of these oxygen heterocycles with nitrogen oxides and other

reagents as a route to nitrate esters.

3.4.1 Ring-opening nitration of epoxides

3.4.1.1 Reaction of epoxides with dinitrogen tetroxide

O

30

HH

CH 2 Cl 2 O

H 2 O

ONO

ONO 2

ONO 2

O ONO^2

2 NO

HO

N 2 O 4

N 2 O 5 or O 3

31

2

32

Figure 3.20

The reaction of epoxides with dinitrogen tetroxide in chlorinated solvents has been studied with

the conclusion that under these conditions dinitrogen tetroxide has only weak nitrating ability.^74

These reactions yield unstable nitrate-nitrite esters which on aqueous work-up undergo hydrol-

ysis to yield the correspondingβ-hydroxy-nitrate ester; 2-nitratoethanol (32) can be formed in

this way from ethylene oxide (30).^75 Nitrate-nitrite esters like (31) undergo efficient oxidation

to the correspondingvic-dinitrate esters on treatment with reagents like ozone and dinitro-

gen pentoxide.^26 ,^75 However, the same transformation of epoxide tovic-dinitrate ester can be

achieved in one step with dinitrogen pentoxide and in much higher yield (Section 3.4.1.2).