Karaghiosoff et al.
The nitrate (20 mmol) was slowly added with stirring to cooled
(ca. -8 °C) concentrated sulfuric acid (4.5 mL). During the addition
of the nitrate the temperature of the reaction mixture should not
exceed 0 °C. After the addition the reaction mixture was stirred
for further 10 min, quickly heated to 25 °C, and poured onto 30 g
of ice. The white crystalline solid was separated by filteration and
washed with water until it became acid free and was recrystallized
from an appropriate (see below) solvent. A second crop of product
was obtained by extracting the aqueous solution with Et2O followed
by the workup procedures described above. Method B; 6a-c. The
method described in11a was used. To cooled acetic anhydride (5 g;
ice bath), 5 g of 100% nitric acid was added dropwise over 10
min. After 20 min, 25 mmol of the respective amino-1H-tetrazole
was added in small portions over 10 min. The solution was stirred
for further 20 min and then quenched on 25 g of crushed ice. The
crude product was collected, washed until it became acid free, and
recrystallized from an appropriate (see below) solvent. Method C;
6a and 6c. To a well stirred suspension of 0.41 mL (15 mmol) of
90% hydrogen peroxide in 10 mL of DCM (cooling with an ice-
bath recommended) was added 2.60 mL (18 mmol) of trifluoroacetic
anhydride in one portion. After 5 min the solution was allowed to
warm to room temperature and 10 mmol of the corresponding
nitrosamine in 5 mL of DCM was added dropwise over a 30-min
period. During this addition an exothermic reaction occurred, which
caused the solution to boil. After the addition was completed the
mixture was heated under reflux for 1 h. The DCM solution was
then washed with water (3 × 15 mL) and dried over MgSO4. The
solvent was removed by distillation under reduced pressure and
the residue was recrystallized from an appropriate (see below)
solvent.
compound shows in solution dynamic behaVior. 1H NMR (d6-
acetone, 25 °C) δ: 1.31 (s, 6H, CH(CH3)2), 1.58 (d, 6H, 3J 6.6 Hz,
-CH(CH3)2), 4.9 (septett, 1H, 3J 6.6 Hz, -CH(CH3)2), 5.07 (septett,
3
1H, J 6.6 Hz, -CH(CH3)2); (d6-acetone, -65 °C) δ: 1.03 (d, 3H,
3J 7.0 Hz, -CH3), 1.45 (d, 3H, 3J 6.4 Hz, -CH3), 1.49 (d, 3H, 3J 6.6
Hz, -CH3), 1.56 (d, 3H, 3J 6.6 Hz, -CH3), 5.05 (septett, 2H, 3J 6.6
Hz, -CH(CH3)2). 13C NMR (d6-acetone, 25 °C) δ: 18.6 (CH3), 21.1
(CH3), 51.3 (CH), 55.5 (CH), 147.0 (C); (d6-acetone, -65 °C) δ:
18.3 (CH3), 18.3 (CH3), 21.6 (CH3), 22.0 (CH3), 50.8 (CH), 54.9
(CH), 146.9 (C). 14N NMR (d6-acetone, 25 °C) δ: 13 (N2, ∆ν1/2
) 666 Hz), -11 (N3, ∆ν1/2 ) 571 Hz), -36 (-iPrN-NO2, ∆ν1/2
)
24 Hz), -56 (N4, ∆ν1/2 ) 435 Hz), -130 (N1, ∆ν1/2 ) 201 Hz),
-200 (-iPrN-NO2, ∆ν1/2 ) 989 Hz); m/z (CI, i-Buten) 215 [(M +
H+) (18)], 210 (15), 196 (15), 170 (100), 169 (18); m/z (DEI) 169
(37), 154 (12), 127 (24), 126 (10), 110 (9), 111 (36), 99 (10), 86
(39), 85 (11), 14 (84), 80 (29), 69 (14), 64 (15), 58 (22), 57 (16),
48 (19), 43 (100), 42 (21), 41 (30), 39 (9). C7H14N6O2 (214.23):
Calcd C, 39.3; H, 6.6; N, 39.2. Found: C, 39.2; H, 6.6; N, 39.4.
7-Nitro-5,6-dihydro-7H-imidazolo[1,2-d]tetrazole (6c). Re-
crystallization from acetone/water. Mp 150 °C (decomp). ν˜(KBr)
[cm-1]: 3035 (vw, -CH2), 3017 (vw, -CH2), 1592 (vs, ν˜asym NO2),
1550 (s, ν˜ (CdN)), 1515 (m), 1472 (m), 1359 (s), 1335 (vs, ν˜ -N-
NdN-+), 1299 (s, ν˜sym NO2), 1276 (m), 1235 (m), 1204 (m, ν˜
tetrazole), 1186 (m, ν˜ tetrazole), 1138 (w, ν˜ tetrazole), 1108 (vw,
ν˜ tetrazole), 1041 (vw, ν˜ tetrazole), 956 (w, ν˜ -CH3N-NO2), 800
(w), 763 (w), 747 (w), 715 (m), 683 (m), 527 (vw). Raman (200
mW) ν˜[cm-1]: 3035 (45), 3018 (33), 2995 (52), 2976 (60), 2933
(12), 2902 (14), 1582 (59), 1552 (100, ν˜asym NO2), 1495 (10), 1471
(37), 1457 (25), 1378 (9), 1363 (18), 1291 (48, ν˜ -N-NdN-+), 1268
(30), 1235 (60, ν˜sym NO2), 1207 (26), 1140 (17, ν˜ tetrazole), 1109
(10, ν˜ tetrazole), 1042 (60, ν˜ tetrazole), 957 (12, ν˜ tetrazole), 935
(21, ν˜ -CH3N-NO2), 801 (90), 763 (8), 719 (7), 683 (23), 527 (31),
1-Methyl-5-(methylnitramino)-1H-tetrazole (6a). Recrystalli-
zation from benzene/pentane. Mp 58-58.5 °C. ν˜(KBr) [cm-1]:
3038 (vw), 2961 (vw, -CH3), 2925 (vw, -CH3), 2854 (vw, -CH3),
1576 (vs, ν˜asym NO2), 1545 (m), 1487 (m), 1461 (m), 1430 (m),
1384 (w), 1314 (m, ν˜ -N-NdN-+), 1294 (s, ν˜sym NO2), 1269 (m),
1214 (m, ν˜ tetrazole), 1181 (m, ν˜ tetrazole), 1127 (m, ν˜ tetrazole),
1093 (m, ν˜ tetrazole), 1049 (w), 989 (w), 949 (m, ν˜ -CH3N-NO2),
786 (m), 761 (m), 748 (w), 606 (m). Raman (200 mW) ν˜[cm-1]:
3038 (33), 3025 (34), 2962 (99), 2829 (9), 1551 (100, ν˜asym NO2),
1488 (14), 1440 (25), 1418 (23), 1315 (27, ν˜ -N-NdN-+), 1291
(33, ν˜sym NO2), 1270 (45, ν˜ tetrazole), 1216 (26, ν˜ tetrazole), 1153
(7, ν˜ tetrazole), 1096 (15), 1051 (8), 991 (10), 951 (38, ν˜ -CH3N-
NO2), 787 (70), 699 (63), 607 (32), 490 (40), 451 (27), 402 (22),
1
441 (29), 402 (42), 326 (22), 213 (29), 122 (21). H NMR (d6-
acetone) AA′BB′-spectrum (δA) 4.85, δB) 5.36, N ) 29 Hz, CH2).
13C NMR (d6-acetone) δ: 42.9 (CH2), 58.2 (CH2), 158.6 (C). 14N
NMR (d6-acetone) δ: 30 (N3, ∆ν1/2 ) 238 Hz), -25 (N2, ∆ν1/2
)
262 Hz), -42 (-RN-NO2, ∆ν1/2 ) 24 Hz), -82 (N4, ∆ν1/2 ) 190
Hz), -158 (N1, ∆ν1/2 ) 142 Hz), -206 (-RN-NO2, ∆ν1/2 ) 476
Hz); m/z (DEI) [(M+) (34)], 111 (30), 98 (11), 55 (70), 54 (100),
53 (59), 52 (30), 46 (45), 40 (13), 30 (53). C3H4N6O2 (156.10):
Calcd: C, 23.1; H, 2.6; N, 53.8. Found: C, 22.7; H, 2.7; N, 53.6.
X-ray Structure Determinations. X-ray quality single crystals
of 3c (CCDC 269260), 5a (CCDC 269261), and 6c (CCDC 269265)
were mounted in a Pyrex capillary, and the X-ray crystallographic
data were collected on a Nonius Mach3 diffractometer with
graphite-monochromated Mo KR radiation (λ ) 0.71073 Å). The
X-ray crystallographic data for 6a (CCDC 269263) and 6b (CCDC
269264) were collected on a STOE IPDS area detector and for 3a
(CCDC 269259) and 5c (CCDC 269262) data were collected on
an Nonius Kappa CCD diffractometer using graphite-monochro-
mated Mo KR radiation (λ ) 0.71073 Å). Unit cell parameters for
3c, 5a, and 6c were obtained from setting angles of a minimum of
15 carefully centered reflections having 2θ > 20°; the choice of
the space group was based on systematically absent reflections and
confirmed by the successful solution and refinements of the
structures. The structures were solved by direct methods (SHELXS-
86, SIR97)56,57 and refined by means of full-matrix least-squares
procedures using SHELXL-97. Empirical absorption correction by
Psi-scans was used for 3c, 5a, and 6c. In the case of 3a, 6a and 6b
numerical absorption correction by XRed was applied.56 Crystal-
1
321 (15), 280 (24), 254 (20), 142 (74). H NMR (d6-acetone) δ:
3.82 (s, 3H, CH3), 4.10 (s, 3H, CH3). 13C NMR (d6-acetone) δ:
29.8 (CH3), 35.7 (CH3), 147.8 (C). 14N NMR (d6-acetone) δ: 10
(N2, ∆ν1/2 ) 578 Hz), -4 (N3, ∆ν1/2 ) 616 Hz), -35 (-CH3N-
NO2, ∆ν1/2 ) 23 Hz), -58 (N4, ∆ν1/2 ) 374 Hz), -155 (N1, ∆ν1/2
) 181 Hz), -219 (-CH3N-NO2, ∆ν1/2 ) 919 Hz); m/z (CI, i-Buten)
159 [(M + H+) (100)]. C3H6N6O2 (158.12): Calcd C, 22.8; H,
3.8; N, 53.2. Found: C, 22.8; H, 3.9; N, 53.4.
1-Isopropyl-5-(isopropylnitramino)-1H-tetrazole (6b). Re-
crystallization from EtOH/water. Mp 56-57 °C. ν˜(KBr) [cm-1]:
2994 (vw, -iPr), 2971 (vw, -iPr), 2883 (vw, -iPr), 2847 (vw, -iPr),
1567 (vs, ν˜asym NO2), 1469 (w), 1461 (w), 1448 (vw), 1426 (m),
1401 (vw), 1391 (w), 1385 (vw), 1375 (vw), 1350 (vw), 1321 (m,
ν˜ -N-NdN-+), 1288 (s, ν˜sym NO2), 1254 (vw), 1243 (vw), 1182
(w, ν˜ tetrazole), 1164 (w, ν˜ tetrazole), 1137 (vw, ν˜ tetrazole), 1125
(m, ν˜ tetrazole), 1091 (w, ν˜ tetrazole), 1062 (w, ν˜ tetrazole), 994
(vw), 970 (w, ν˜ -CH3N-NO2), 946 (vw), 934 (vw), 885 (vw), 792
(w), 760 (w), 736 (vw), 726 (vw), 668 (vw), 643 (vw), 589 (vw),
555. Raman (200 mW) ν˜[cm-1]: 2999 (100), 2990 (84), 2974 (80),
2946 (93), 2929 (69), 2875 (28), 2773 (6), 2733 (11), 1576 (12),
1522 (83, ν˜asym NO2), 1457 (53), 1398 (29), 1322 (21), 1285 (40,
ν˜ -N-NdN-+), 1253 (41, ν˜sym NO2), 1183 (17, ν˜ tetrazole), 1138
(29, ν˜ tetrazole), 1092 (39, ν˜ tetrazole), 1068 (29, ν˜ tetrazole), 1048
(12), 994 (12), 948 (24, ν˜ -CH3N-NO2), 888 (45), 795 (60), 767
(12), 735 (10), 646 (42), 588 (19), 564 (19), 477 (41), 439 (49),
377 (17), 349 (34), 317 (24), 295 (24), 152 (84), 119 (44). The
(56) (a) Sheldrick, G. M. SHELXL-86, Program for Solution of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1986. (b)
Sheldrick, G. M. SHELXL-97, Program for Solution of Crystal Structures;
University of Go¨ttingen: Go¨ttingen, Germany, 1997. (c) Gabe, E. J.; Le
Page, Y.; Charland, J.-P.; Lee, F. L.; White, P. S. J. Appl. Crystallogr.
1989, 22, 384. (d) XRed, rev. 1.09; Darmstad Germany.
(57) Altomare, A.; Burla, M. C. M.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
1304 J. Org. Chem., Vol. 71, No. 4, 2006