Kvaskoff et al.
δ 9.38 (s, 1 H), 8.65 (d, J ) 8 Hz, 1 H), 8.21 (d, J ) 8 Hz, 1 H),
8.15 (t, J ) 8 Hz, 1 H), 7.87 (t, J ) 8 Hz, 1 H); 1H NMR (CDCl3-
CF3COOH (1:1)) (minor isomer 10) δ 9.77 (s, 1 H), 8.80 (d, 1 H),
8.50 (d, 1 H), 8.40 (t, 1 H), 8.10 (t, 1 H); (major isomer 9) δ 9.73
(s, 1 H), 8.35 (d, 1 H), 8.30, (t, 1 H), 8.05 (d, 1 H), 7.95 (t, 1 H);
ratio 10:9 ) 21:79; 13C NMR (CDCl3) δ 160.8 (CH), 151.6 (C
quart), 136.2 (CH), 130.9 (C quart), 129.3 (CH), 128.9 (CH), 117.8
(C quart), 114.1 (CH) ppm; the assignments are supported by a
DEPT-135 spectrum. The Ar matrix IR spectrum is shown in Figure
S1. Anal. Calcd for C8H5N5: C, 56.14; H, 2.94; N, 40.92. Found:
C, 55.99; H, 2.79; N, 40.86.
Semipreparative FVT of Azide 9. Experimental conditions for
the FVT of 9 and matrix isolation of the products were as described
above. After the ESR experiments, the copper rod was rinsed with
dichloromethane (2 mL) and the products were analyzed by GC-
MS to give the following composition: tetrazole 9 (60% at 430
°C, 0% at 600 °C, Rt ) 9.43 min, m/z ) 171), 2-aminoquinazoline
(23) (11% at 430 °C, 35% at 600 °C, Rt ) 7.36 min, m/z ) 145),
21 (28% at 430 °C, 65% at 600 °C, Rt ) 5.96 min, m/z ) 143),
and indazole (24) (0.6% at 430 °C, 1.8% at 600 °C, Rt ) 5.66
min, m/z ) 118), all identified by comparison with the authentic
materials.
Matrix Isolation of Azide 10. 9 (ca. 10 mg) was sublimed at
105 °C through an external quartz oven (200-230 °C for photolysis
experiments, 430-600 °C for FVT) under vacuum (2.0 × 10-6
mbar) and codeposited with Ar (5 mbar/min from a 2 L reservoir
filled with 1 atm of Ar). The Ar matrix IR spectrum is shown in
Figure S2.
1-Cyano-3-phenylindazole (31). Tetrazole 25/azide 26 (mp
202-203 °C; 0.45 g, 1.82 mmol) was subjected to preparative FVT
at 380 °C in the course of 4 h. The resulting product was sublimed
at 65-75 °C/10-3 mbar to afford 0.25 g (63%) of white, slightly
lachrymatory crystals of 31; mp 95-96 °C; very soluble in ether;
MS m/z 219; IR (KBr) 2255, 1640 cm-1; IR (Ar, 10 K) 2256 vs,
1617 w, 1495 m, 1365 s, 1357 m, 1150 w, 1111 w, 1064 m, 783
m, 769 w, 745 m, 697 m, 579 w cm-1. Anal. Calcd for C14H9N3:
C, 76.70; H, 4.11; N, 19.18. Found: C, 76.64; H, 4.22; N, 19.22.
A 0.02 g portion of 31 was hydrolyzed with 5 mL of 0.2 N
NaOH at 125 °C for 3 h. After the solution was cooled to room
temperature, the precipitate was filtered off, and the solution was
neutralized and extracted with EtOAc. The extract was evaporated
to dryness, and the resulting solid was recrystallized from petroleum
ether or sublimed at 100 °C/10-2 mbar to afford 3-phenylindazole:
mp 114-116 °C (lit.26 mp 115-116 °C).
Matrix Photolysis of Tetrazolo[1,5-a]quinazoline/2-Azi-
doquinazoline (9/10). The matrix photolysis of tetrazole 9/azide
10 yielded 1-cyanoindazole (21) and N-cyanoanthranilonitrile (22).
A brief photolysis of 10 (Ar, 10 K, 308 nm, 30 s) afforded species
21 absorbing at 2260 cm-1. In the course of further photolysis
another new species rapidly grew in at 2255 cm-1, and this was
the main species after long photolysis times (25 h) with 254 nm.
Complete conversion of azide to 22 was not possible even after 2
days of photolysis with 308, 254, and 222 nm. Bands due to 22
are at 3411, 3406 w, 2255 w (NHCN), 2236 vw (CN), 1595 m,
1511 m, 1439 w, 1306 w, 1256 vw, 1167 vw, and 757 m cm-1
.
Matrix Isolation of Azide 26. Tetrazole 25 was sublimed at
150 °C, and the vapor was passed through the FVT tube at 200 °C
and then deposited with Ar at 22 K. IR (Ar, 10 K): 2174 w, 2137
s, 2131 s, 2109 w, 1620 m, 1569 m-s, 1552 s, 1543 s, 1327 vs,
1-Cyanoindazole (21). Sodium hydride (90 mg, 3.75 mmol) was
added to a solution of 413 mg (3.5 mmol) of indazole in 30 mL of
toluene, and the mixture was stirred for 1 h. Cyanogen bromide
(556 mg, 5.2 mmol) in 10 mL of toluene was added dropwise, and
the resulting mixture was refluxed for 3 h. After filtration and
removal of the solvent and excess BrCN in vacuo, the resulting
product was sublimed at 55-60 °C (10-2 mbar) to afford 300 mg
1265 m, 1233 m, 777 w, 699 m, 636 w cm-1
.
Acknowledgment. This work was supported by the Aus-
tralian Research Council, the APAC national supercomputing
facility (merit allocation scheme), and the Centre for Compu-
tational Molecular Science at The University of Queensland.
We thank Dr. Michael Kiselewski for preliminary experiments
and calculations, Mr. Riko Burgard for assistance with some
experiments, and Dr. Tri Le and Mr. George Spatny for untiring
help keeping the ESR spectrometer running.
1
(60%) of 21: mp 70-72 °C; H NMR (CDCl3) δ 8.23 (s, 1 H),
7.80 (d, 1 H, J ) 8 Hz), 7.67 (t, 1 H, J ) 7 Hz), 7.64 (t, 1 H, J )
8 Hz), 7.41 (t, 1 H, J ) 7 Hz); MS m/z ) 143. The Ar matrix IR
spectrum is shown in Figure S11. Anal. Calcd for C8H5N3: C,
67.13; H, 3.50; N, 29.37. Found: C, 67.03; H, 3.43; N, 29.41.
21 by Preparative FVT of Azide 9. Tetrazole 9 (100 mg) was
subjected to preparative FVT at 600 °C. The product was isolated
in a liquid N2 trap and purified by column chromatography on silica
gel and sublimation at 55-60 °C (10-2 mbar) to afford 21 (62%),
mp 70-72 °C, with properties identical with those described above.
Matrix Isolation of 21. Tetrazole 9/azide 10 was sublimed into
the FVT tube in a stream of Ar at 106-108 °C and thermolyzed at
500 °C. The products were isolated in an Ar matrix at 20 K, and
FTIR spectra were recorded at ca. 10 K. A typical IR spectrum of
the thermolysis product 21, and the calculated spectrum, together
with the spectrum of authentic material, is shown in Figure S11.
Bands due to 21 (Ar, 10 K) are at 2260 s (CN), 1618 vw, 1507 w,
1429 m, 1373 w, 1149 vw, 1027 w, 908 w, 748 m, and 746 m
Supporting Information Available: Experimental and calcu-
lated IR spectra, D-F correlation for over 100 nitrenes, ESR spectra
of nitrenes, diradicals, and carbene 37, kinetics of decay of triplet
diradical at 15 K, UV-vis spectrum of 33, Cartesian coordinates,
absolute energies, and frequencies or electronic transitions of
compounds calculated at the B3LYP/6-31G**, B3LYP/6-31G*,
TDB3LYP/6-31G**, and CASSCF(8,8)/6-31G* or CASPT2 levels,
and structures and spin densities of triplet nitrenes and diradicals
19a-c (UB3LYP/EPRIII). This material is available free of charge
cm-1
.
JO052541I
4058 J. Org. Chem., Vol. 71, No. 11, 2006