Organic Chemistry of Explosives

24 Synthetic Routes to AliphaticC-Nitro

(69) is formed in 85 % yield via the oxidation of the corresponding bis-isocyanate (81) with

dimethyldioxirane in wet acetone.^189 Similar chemistry has been used to prepare 1,3,5,7-

tetranitrocubane and 1,3-dinitrocubane from the corresponding isocyanates (see Section

2.4).^190 Although dimethyldioxirane is a very efficient reagent for the oxidation of aliphatic iso-

cyanates to nitro compounds, it has been relatively unexplored. These reactions are only limited

by the lack of available methods for isocyanate formation and their commercial availability.

1.6.6 Oxidation of nitrosoalkanes

Nitroso compounds are formed during the addition of nitrous oxide,^48 ,^49 dinitrogen

trioxide,^48 ,^49 and nitrosyl halides^50 to alkenes, and in some cases, from incomplete oxidation

of amines^166 with peroxyacids like peroxyacetic acid. Quenching of carbanions with nitrosyl

halides is also a route to nitroso compounds.^190 A full discussion on this subject is beyond the

scope of this work and so the readers are directed to the work of Boyer.^191

Oxidation of aliphatic nitroso functionality is usually facile but is not widely used

in energetic materials synthesis. The following reagents have been used in these

conversions: oxygen,^192 hydrogen peroxide,^193 nitrous oxide,^194 dinitrogen tetroxide,^195

chromium trioxide,^196 alkaline permanganate,^197 alkaline hypochlorite,^198 ozone,^166 ammo-

nium persulfate,^198 peroxyacids^199 etc.^190

1.7 Kaplan–Shechter reaction

R 2 C

N

Ag

ON

O

O

O

R 2 C

R 2 C(NO 2 ) 2

Ag

AgNO 2

+ 2 Ag^0

82

NO 2 Ag

Figure 1.34 Proposed mechanism for oxidative nitration (ref. 105)

Oxidative nitration, a process discovered by Kaplan and Shechter,^105 is probably the most ef-

ficient and useful method available for the synthesis ofgem-dinitroaliphatic compounds from

the corresponding nitroalkanes. The process, which is an electron-transfer substitution at satu-

rated carbon, involves treatment of the nitronate salts of primary or secondary nitroalkanes with

silver nitrate and an inorganic nitrite in neutral or alkali media. The reaction is believed^105 ,^200

to proceed through the addition complex (82) which collapses and leads to oxidative addition

of nitrite anion to the nitronate and reduction of silver from Ag+^1 to Ag^0. Reactions proceed

rapidly in homogeneous solution between 0 and 30◦C.

CH 3 CH 2 NO 2

22

1. NaOH (aq)

NO 2

C

NO 2

CH 3 CH 2 OH

25

2. NaNO 2 , 2 AgNO 3


3. AcOH, CH 2 O
   80 % (3 steps)

Figure 1.35