Organic Chemistry of Explosives

Nitrate esters from strained oxygen heterocycles 101

co-workers^75 found it necessary to add aluminium chloride to the reaction mixtures of some

substrates. Glycidol (18) and butadiene diepoxide (36) react with dinitrogen pentoxide in the

presence of 1.0 mole equivalent of aluminium chloride to give nitroglycerine (1) and erythritol

tetranitrate (9) respectively (Table 3.2, Entries 4 and 5). The synthesis of erythritol tetranitrate

via this method is attractive because the scarcity of erythritol prevents its direct nitration with

mixed acid on an industrial scale.

Research efforts are ongoing into the use of dinitrogen pentoxide for the industrial syn-

thesis of nitrated hydroxy-terminated polybutadiene (NHTPB) from epoxidated HTPB (Sec-

tion 3.10).^76 The reaction of aziridines with dinitrogen pentoxide is an important route to

1,2-nitramine-nitrates and these reactions are discussed in Section 5.8.1.^77

3.4.1.3 Reaction of epoxides with nitrate anion under acidic conditions

O

30

HH

32

HNO 3 (aq), NH 4 NO 3

or HNO 3 , CHCl 3

58 %

HO

ONO 2

Figure 3.21

Nichols and co-workers^78 ,^79 studied the formation ofβ-hydroxy nitrate esters via the acid-

catalyzed ring-opening of epoxides with nitrate anion. Reactions were conducted in aqueous

media using solutions of ammonium nitrate is nitric acid and under nonaqueous conditions

using solutions of pure nitric acid in chloroform. 2-Nitratoethanol (32) is formed in∼58 %

yield from ethylene oxide (30) using either of these methods.^78

O

39

HR HNO

3 (aq), NH 4 NO 3

+

40

O 2 NO

OH

R

41

HO

ONO 2

R

Figure 3.22

Unsymmetrical epoxides (39) can form two isomers, (40) and (41), on reaction with nitrate

anion and so raise the issue of regioselectivity. Under acidic conditions terminal epoxides are

found to predominantly yield the primary nitrate ester (41); although this is not clear cut and

propylene oxide is reported to yield an ill defined mixture of isomers.^78 A comprehensive

study on the regioselectivity of epoxide opening with nitrate anion under acidic conditions was

conducted on glycidol.^79

3.4.1.4 Single electron transfer nitration of epoxides with ceric ammonium nitrate

O

R

R = ClCH 2 -, 80 %

R = PhOCH 2 -, 98 %

R = CH 2 =CHCH 2 OCH 2 -, 88 %

R = (CH 3 ) 2 CHOCH 2 -, 88 %

CAN, NH 4 NO 3

CH 3 CN, 80 °C R

ONO 2

OH

Figure 3.23