Organic Chemistry of Explosives

102 Synthetic Routes to Nitrate Esters

Ceric ammonium nitrate (CAN) has been used for the synthesis ofβ-hydroxy nitrate esters from

epoxides.^80 −^82 These reactions are performed in the presence of nitrate sources like ammonium

nitrate orn-tetrabutylammonium nitrate, or with CAN alone, in acetonitrile between room tem-

perature and reflux.^80 ,^81 Yields ofβ-hydroxy nitrate esters are high to excellent for a range

of epoxide substrates. Reactions are generally very stereoselective for unsymmetrical epox-

ides carry either activating or deactivating groupsαto the epoxy group; epichlorohydrin and

3-phenoxy-1-epoxypropane both react to give the primary nitrate esters.^80 Poor selectivity is

observed for unsymmetrical epoxides where electronic and steric effects are counterbalanced

i.e. for 1-epoxypropane.^80 Lower yields are realized for more hindered epoxides and tertiary

centres can lead to undesirable side-reactions.^81

3.4.1.5 Other reactions

A suspension of thallium (III) nitrate in hexane reacts with epoxides to give the corresponding

β-hydroxy nitrate esters in good yield.^83 The same reagent in acetonitrile has been used to syn-

thesizeα-nitratoketones^84 from substituted acetophenones, 1,2-dinitrate esters from alkenes,^85

and 1,3-dinitrates from ring-opening nitration of cyclopropanes.^85

3.4.2 1,3-Dinitrate esters from the ring-opening nitration of oxetanes

with dinitrogen pentoxide

O

H

H

R^2 R^3

R^1

H

CH 2 Cl 2

CCC

H^3 HR

R^1 R^2 H

O 2 NO ONO 2

N 2 O 4

R^1 , R^2 , R^3 = H, 88 %

R^1 = H, R^2 , R^3 = Me, 73 %

R^1 = H, R^2 , R^3 = - (CH 2 ) 5 -, 86 %

R^1 = Me, R^2 , R^3 = Et, 17 %

Figure 3.24

Millar and co-workers^86 studied the ring-opening nitration of oxetanes with dinitrogen pentox-

ide as a route to 1,3-dinitrate esters. Oxetane reacts with dinitrogen pentoxide in a chlorinated

solvent to give 1,3-propanediol dinitrate in high yield but with some oligomeric material

formed. 3,3-Disubstituted oxetanes are slower to react and produce more oligomeric material

(5–30 %) but still give moderate to high yields of 1,3-dinitrate ester. Yields are much lower if

the oxetane substrate contains 2-alkyl substituents.

O

42

3 C CH 2 OHH

O

43

(NIMMO)

H 3 C CH 2 ONO 2

H 3 C

CH 2 ONO 2

CH 2 ONO 2

CH 2 ONO 2

4

2.46 eq N 2 O 5 ,

CHCl 3 , 0.5 hr

-10 to 0 °C

62 %

4.0 eq N 2 O 5 ,

CHCl 3 , 28 hr

-10 to +15 °C

88 %

C

Figure 3.25

The reaction of 3-hydroxymethyl-3-methyloxetane (42) with dinitrogen pentoxide is an

interesting example; a short reaction time with 2.46 equivalents of dinitrogen pentoxide pro-

ducing 3-(nitratomethyl)-3-methyloxetane (NIMMO) (43), an energetic polymer precursor,