Organic Chemistry of Explosives

206 Synthetic Routes toN-Nitro

CH 3

NO 2

NH 2

50

O 2 N

CH 3

NO 2

NO 2

NHNO 2

51

20 °C, 55 %

NO 2 BF 4 ,

ClCH 2 CH 2 Cl O^2 N

Figure 5.26

and 4-amino-2,6-dinitrotoluene (50) react with nitronium tetrafluoroborate to giveN,2,4,6-

tetranitroaniline (85 %)^50 and 4-amino-N,2,3,6-tetranitrotoluene (51) (55 %)^51 respectively.

Simple primary aliphatic amines give a low yield of the corresponding nitrate ester through

deamination;n-butylamine gives a 20 % yield ofn-butyl nitrate on treatment with nitronium

tetrafluoroborate in acetonitrile.^46

Ridd and Yoshida^52 explored theN-nitration of aromatic nitroanilines with nitronium hex-

afluorophosphate in nitromethane with the aim of studying the Bamberger rearrangement

(Chapter 4, Section 4.5). In was found that amines of low basicity essentially undergo com-

pleteN-substitution if the amine is in excess; 2,4-dinitroaniline and 2,3-dinitroaniline form

N,2,4-trinitroaniline andN,2,3-trinitroaniline, respectively, as the sole products. More basic

nitroanilines give mixtures ofC-substituted,N-substituted and poly-substituted materials.

The use of nitronium salts forN-nitration has been extensively reviewed.^53 ,^54

5.3.2.7 Transfer nitration

The efficientN-nitration of secondary amines has been achieved by transfer nitration with

4-chloro-5-methoxy-2-nitropyridazin-3-one, a reagent prepared from the nitration of the par-

ent 4-chloro-5-methoxypyridazin-3-one with copper nitrate trihydrate in acetic anhydride.^55

Reactions have been conducted in methylene chloride, ethyl acetate, acetonitrile and diethyl

ether where yields of secondary nitramine are generally high. Homopiperazine is selectively

nitrated toN-nitrohomopiperazine orN, N′-dinitrohomopiperazine depending on the reaction

stoichiometry.N-Nitration of primary amines or aromatic secondary amines is not achievable

with this reagent.

5.3.2.8 Other N-nitrating agents

Other reagents have been used for the direct nitration of amines under nonacidic condi-

tions. Mandel^56 reported the synthesis of methylnitramine, dimethylnitramine and diisopropy-

lnitramine from the reaction of nitryl fluoride with the parent amine. The presence of an excess

of amine appears to be of prime importance given that other reports give the nitrosamine as a

major by-product.^37

Nitryl chloride^57 and tetranitromethane^58 alsoN-nitrate amines. However, competing

N-nitrosation is a particular problem and results from a redox reaction between the nitrat-

ing agent and the amine.

A solution of tetra-n-butylammonium nitrate and triflic anhydride in methylene chloride is

reported to give a 43 % yield ofN-nitropyrrolidine from pyrrolidine.^59 This reagent has been