Regioselective arylation of NH-tetrazoles [5]

Full text of DOI:10.1023/A:1017579704993

Chemistry of Heterocyclic Compounds, Vol. 37, No. 3, 2001
REGIOSELECTIVE ARYLATION
OF NH-TETRAZOLES
V. Yu. Zubarev, S. M. Putis, and V. A. Ostrovskii
Keywords: bis(4-methoxyphenyl)iodonium bromide, 5-phenyltetrazole, arylation.
Reactions of 5-substituted tetrazoles with various electrophilic reagents are generally used in synthesis
of N-alkyltetrazoles [1]. The use of this route to obtain N-aryltetrazoles does not lead to the desired result,
which can be achieved only by more complicated methods [2]. An exception is the attempt to carry out arylation
of the sodium salt of 5-phenyltetrazole with diaryliodonium salts, leading to formation of a complex mixture of
isomeric products [3]. As noted by the authors themselves of the cited paper, this is a consequence of competing
reactions of the diaryliodonium halide with the solvent (t-BuOH). Following the patent in [4], we attempted to
alter the reaction conditions, using the triethylammonium salt of 5-phenyltetrazole in methanol in the reaction
with bis(4-methoxyphenyl)iodonium bromide.
Ph
+
Ph
–
N
N
H
N
Br
OMe
MeO
I
N
N
N
N
N
MeOH / Et3N / Cu / 24 h
OMe
In contrast to [3], in this case we observe selective formation of 2-(4-methoxyphenyl)-5-phenyltetrazole.
The method described possibly is competitive with the traditional methods for obtaining N-aryltetrazoles.
2-(4-Methoxyphenyl)-5-phenyltetrazole. A solution of 5-phenyltetrazole (1.45 g, 10 mmol),
bis(4-methoxyphenyl)iodonium bromide (8.42 g, 20 mmol), triethylamine (1.4 ml, 10 mmol) and copper powder
(0.1 g, 1.5 mmol) in 100 ml anhydrous methanol were stirred for 24 h at 18-20°C. The suspension formed was
filtered to remove a small amount of undissolved material, and then the methanol was evaporated under vacuum.
The residue was dissolved in chloroform (100 ml), washed with a 5% solution of sodium bicarbonate
(3 × 20 ml), distilled water (2 × 25 ml), and dried over sodium sulfate. The chloroform was evaporated under
vacuum, and the dry residue was recrystallized from ethanol. Yield 0.40 g (16%) of 2-(4-methoxyphenyl)-5-
phenyltetrazole; mp 100.5-101.0°C (according to data in ]5], mp 101-102°C; for the analogous 1H-isomer,
1
according to data in [6], mp 130-132°C). Rf 0.75 (Merck 60 F254, 100% chloroform). H NMR spectrum
(DMSO-d6, 300 MHz), , ppm, J (Hz): 8.12 (2H, d, J = 4.4, Ph); 8.02 (2H, d, J = 8.7, Ar); 7.56 (3H, s, Ph); 7.17
δ
(2H, d, J = 8.0, Ar); 3.84 (3H, s, OCH3). 13C NMR spectrum (DMSO-d6, 75 MHz), , ppm: 165.1 (C(5) in
δ
2,5-tetrazole), 131.6, 130.4, 130.1, 127.4, 122.3, 115.9 (Ph and Ar), 56.5 (OCH3). IR spectrum (KBr), , cm-1:
ν
1609, 1596 (Ph and Ar), 1515, 1450, 1263, 1018 (tetrazole ring), 829, 726, 687. Found, %: C 66.53; H 4.70;
N 22.30. C14H12N4O. Calculated, %: C 66.65; H 4.79; N 22.21.
____________________________________________________________________________________________
St. Petersburg State Technology Institute (Technical University), St. Petersburg 198013, Russia; e-mail:
ostrovskii@mail.convey.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 400-401,
March, 2001. Original article submitted November 16, 2000.
372
0009-3122/01/3703-0372$25.00©2001 Plenum Publishing Corporation

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