evaporation of the solvent, 1-(4-fluorophenyl)-4-(1-phenylprop-
2-en-1-yl)-1,4-dihydrotetrazol-5-one 2a was isolated as a colourless
oil (0.29 g, 98%) (Found: C, 64.8; H, 4.4; N, 18.8. C16H13FN4O
requires C, 64.9; H, 4.4; N, 18.9%); dH (CDCl3) 5.26–5.52 (m, 2 H),
6.0 (d, 1 H, J 5.7 Hz), 6.39–6.55 (m, 1 H), 7.12–7.50 (m, 7 H),
7.90–8.0 (m, 2 H); vmax/cmꢀ1 1729, 1605, 1511, 1386, 1233 and 723;
m/z 296 (Mǹ).
(ii) Similarly, 1-phenyl-4-(but-3-en-2-yl)-1,4-dihydrotetrazol-5-one
2b was prepared from the tetrazole 1b and was isolated as a colour-
less oil (98% yield) (Found: C, 61.0; H, 5.6; N, 26.1. C11H12N4O
requires C, 61.1; H, 5.6; N, 25.9%); dH (CDCl3) 1.65 (d, 3 H, J 5.7
Hz), 4.9–5.1 (m, 1 H), 5.22–5.4 (m, 2 H), 6.0–6.2 (m, 1 H),
7.3–7.55 (m, 3 H), 7.95 (d, J 8.6 Hz); vmax/cmꢀ1 1729, 1599, 1504,
1382 and 757; m/z 216 (Mǹ).
Cross-over Experiment.sA mixture of 1b (0.044 g, 0.2 mmol)
and 1a (0.060 g, 0.2 mmol) in 1,1,2,2-tetrachloroethane (4 ml) was
heated at 100 °C for 4 h. The product was isolated by evaporation
of the solvent to give an oily residue which was subjected to mass
spectrometry (EI). Molecular ion peaks in the mass spectrum at
m/z 296 and 216 were observed, corresponding to the molecular
ions of the two tetrazolones 2a,b resulting from rearrangement of
the tetrazoles, but no peaks were observed at m/z 234 or 278 that
would correspond to cross-over. The appearance of the mass spec-
trum resulting from heating the mixture of tetrazoles 1a,b was
identical with that produced by an authentic mixture of the N-allyl-
tetrazoles 2a,b.
Experimental
Melting points were recorded on a Reichert microscopic appara-
tus and are uncorrected. Mass spectra were obtained on a VG
7070E mass spectrometer by electron ionization (EI), at 70 eV. IR
spectra were recorded on a Perkin Elmer 1720X FT-IR spectro-
meter, liquids as films and solids as KBr disks. NMR spectra were
recorded either on a Bruker WM 250 MHz FT or on a Bruker AC
200 FT spectrometer, using tetramethylsilane as internal standard.
Solvents, diethyl ether and tetrahydrofuran, were freshly dried by
refluxing them over sodium diphenylketyl prior to use. Other
chemicals were used as purchased.
Preparation of Tetrazoles 1a,bs(i) A slow stream of chlorine was
bubbled through a solution of 4-fluorophenyl isothiocyanate (2 g,
14.8 mmol) in CH2Cl2 (40 mL) for 24 h. The solution was then
purged of excess of chlorine by nitrogen gas, filtered and the filtrate
concentrated to give N-(4-fluorophenyl)-1,1-dichloroazomethine
as a colourless liquid (2.25 g, 79%); dH (CDCl3) 7.0–7.2 (m); vmax
/
cmꢀ1 1651, 1502, 1232, 897 and 833. This product was used without
further purification. Activated sodium azide (0.12 g, 1.9 mmol) was
added to the N-(4-fluorophenyl)-1,1-dichloroazomethine (0.31 g,
1.61 mmol) in 1,2-dimethoxyethane (5 mL) and the mixture was
stirred at room temperature for 36 h. The resulting sodium chlor-
ide was filtered off and the filtrate was evaporated to afford a
colourless solid, which was recrystallized from benzene–ethanol
(1:1) to give colourless crystals of the required 5-chloro-1-(4-
fluorophenyl)-1H-tetrazole (0.25 g, 78%), mp 85–86 °C (lit.,7
88 °C) (Found: C, 42.5; H, 2.0; N, 28.1. Calc. for C7H4ClFN2: C,
42.3; H, 2.0; N, 28.2%); dH (CDCl3) 7.2–7.4 (m, 2 H), 7.5–7.7 (m,
2 H); m/z 198, 200 (Mǹ, 3:1, Cl isotopes). A mixture of (E)-3-phe-
nylprop-2-en-1-ol (cinnamyl alcohol; 0.15 g, 1 mmol) and sodium
hydride (0.048 g, 1.6 mmol) in THF (10 mL) was stirred at room
temperature until effervescence had ceased, at which stage a solu-
tion of 5-chloro-1-(4-fluorophenyl)-1H-tetrazole (0.2 g, 1 mol) in
THF (5 mL) was added. After the mixture had been stirred for a
further 2 h, the reaction was worked up by addition of ice–water
(30 mL) and extraction with diethyl ether. After drying (Na2SO4),
evaporation of solvent and ‘flash’ chromatography on silica gel with
CH2Cl2 as eluent, colourless crystals of 1-(4-fluorophenyl)-
5-[(E)-3-phenylprop-2-en-1-yloxy)-1H-tetrazole 1a were isolated
(0.11 g, 37%), mp 83–85 °C (Found: C, 65.2; H, 4.5; N, 18.7.
C16H13FN4O requires C, 64.9; H, 4.4; N, 18.9%): dH (CDCl3) 5.25
(d, 2 H, J 6 Hz), 6.4-6.6 (m, 1 H), 6.9 (d, 1 H, J 14.8 Hz), 7.2–7.6 (m,
7 H), 7.6–7.8 (m, 2 H); vmax/cmꢀ1 1563, 1514, 1367 and 1232; m/z
296 (Mǹ).
We gratefully acknowledge the financial assistance to
M. L. S. C. of JNICT (Portugal) and of the Eschenmoser
Trust.
Received, 11th December 1996; Accepted, 21st January 1997
Paper E/6/08333A
References
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(ii) (E)-But-2-en-1-ol (crotyl alcohol; 1.0 g, 13.9 mmol) in dry
THF (20 mL) was added to a slurry of sodium hydride (0.6 g, 14.6
mmol) in dry THF (20 ml) and the mixture was stirred at room
temperature under nitrogen until effervescence had ceased (30
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61.1; H, 5.6; N, 25.9%); dH (CDCl3) 1.75 (d, 3 H, J 8.7 Hz), 5.05 (d,
2 H, J 7.9 Hz), 5.7–5.9 (m, 1 H), 5.9–6.1 (m, 1 H), 7.4–7.6 (m, 3 H),
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N-Allyltetrazolones 2a,b.—(i) The tetrazole 1a (0.3 g, 1 mmol)
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