O
R1
N
O
R1
100% HNO3
TFAA, MeNO2
X1
R1
X1
R1
R2
R2
N
O
N
N
N
R1
R1
N
0 to 50 oC
X2
R2
6
R1=C3H7, X1=COC2H5, X2=NO2
R1=C3H7, X1=NO2, X2=COC2H5
R1=C3H7, X1=COCH3, X2=NO2
R1=C3H7, X1=NO2, X2=COCH3
3
4
5
R1=C3H7, R2=C2H5
R1=C3H7, R2=CH3
R1=H, R2=C2H5
7
8
9
10
11
12
R1=C3H7, X1 and X2 = NO2
R1=H, X1=COC2H5; X2=NO2
R1=H, X1=NO2, X2=COC2H5
R1=H, X1 and X2 = NO2
1
Scheme 1. Nitrolysis of hexahydro-1,3,5-triacyl-s-triazines by TFAN generated in situ.
Results and discussion
To set a baseline for nitrolysis, the tripropionamides syn,syn–3 and 5 were each reacted in 100%
nitric acid (20 molar equivalents) at room temperature for twenty-four hours. Nitrolysis occurred in the
case of 5 which gave a 1:1 mixture consisting of the mono- and dinitramines 11 and 12 along with a
trace of 1. However, syn,syn–3 was recovered from this reaction unchanged. Clearly, the ring propyl
groups of syn,syn–3 completely blocked nitrolysis by nitric acid and a stronger reagent was necessary. A
solution of TFAN was generated at 0 °C in nitromethane by reaction of one equivalent 100 % nitric acid
with 1.6 equivalents of 1,1,1-trifluoroacetic anhydride (TFAA).28–29 This ratio was maintained in all the
nitrolysis experiments in this study to minimize the amount of free mineral acid in the reaction mixtures.
Thus, the nitrolysis medium was most likely a mixture of TFAN, 1,1,1-trifluoroacetic acid (TFA), TFAA and
nitromethane but we did not pursue 19F nuclear magnetic resonance (NMR) or other spectroscopic
analysis of the medium. The tripropionamide syn,syn–3 was added while the mixture was cold and then
stirred at room temperature for several hours. With two equivalents TFAN the nitrolysis of syn,syn–3
gave mononitramine syn,syn–6 and dinitramine syn,syn–7 products in a 3:2 ratio, respectively. With six
equivalents TFAN, nitrolysis of syn,syn–3 gave mostly syn,syn–6 and syn,syn–7 in a 1:9 ratio,
respectively. Careful thin-layer chromatographic (TLC) analysis of the latter product mixture showed a
trace component slightly less polar than dinitramine syn,syn–7. The trace product was roughly purified
by silica gel chromatography and, although contaminated with syn,syn–7, indeed had the expected
triplet resonance of the ring protons of trinitramine syn,syn–10 at ~7.8 ppm, overlapping the
corresponding signal from dinitramine syn,syn–7.