1724
T. M. Potewar et al. / Tetrahedron Letters 48 (2007) 1721–1724
high polarity in addition to its function as a reaction
medium thus obviating the necessity of using any addi-
tional catalyst.
10. (a) Welton, T. Chem. Rev. 1999, 99, 2071; (b) Wasser-
scheid, P.; Keim, W. Angew. Chem., Int. Ed. 2000, 39,
3
773; (c) Sheldon, R. Chem. Commun. 2001, 2399; (d)
Wilkes, J. S. Green Chem. 2002, 4, 73; (e) Jain, N.; Kumar,
A.; Chauhan, S.; Chauhan, S. M. S. Tetrahedron 2005, 61,
In conclusion, we have developed a mild, convenient,
and efficient protocol for the synthesis of 1-substi-
tuted-1H-1,2,3,4-tetrazoles via the condensation of
amines, triethyl orthoformate, and sodium azide using
1
015.
1
1
1. Boon, J. A.; Levinsky, J. A.; Pflug, J. I.; Wilkes, J. S. J.
Org. Chem. 1986, 51, 480.
2. (a) Palimkar, S. S.; Siddiqui, S. A.; Thomas, D.; Lahoti,
R. J.; Srinivasan, K. V. J. Org. Chem. 2003, 68, 9371; (b)
Gholap, A. R.; Venkatesan, K.; Thomas, D.; Lahoti, R.
J.; Srinivasan, K. V. Green Chem. 2004, 6, 147; (c) Nadaf,
R. N.; Siddiqui, S. A.; Thomas, D.; Lahoti, R. J.;
Srinivasan, K. V. J. Mol. Catal. A: Chem. 2004, 240,
1
7
a RTIL as a recyclable medium as well as a promoter.
The process gave rise to excellent isolated yields of 1-
substituted-1H-1,2,3,4-tetrazoles in short reaction times
(
15–35 min).
1
55; (d) Siddiqui, S. A.; Narkhede, U. C.; Palimkar, S. S.;
Thomas, D.; Lahoti, R. J.; Srinivasan, K. V. Tetrahedron
005, 61, 3539; (e) Siddiqui, S. A.; Potewar, T. M.; Lahoti,
Acknowledgement
2
R. J.; Srinivasan, K. V. Synthesis 2006, 2849; (f) Siddiqui,
S. A. Synlett 2006, 155, and references cited therein.
3. Perrin, D. D. Ionization Constant of Inorganic Acids and
Bases in Aqueous Solution, 2nd ed.; Pergamon: Elmsford,
New York, 1982.
4. Fletcher, K. A.; Storey, I. A.; Hendricks, A. E.; Pandey, S.
Green Chem. 2001, 3, 210.
5. Sauer, J.; Huisgen, R.; Strum, H. J. Tetrahedron 1960, 11,
T.M.P., S.A.S. thanks the CSIR, New Delhi, for the
award of Senior Research Fellowship.
1
Supplementary data
1
1
1
13
Supplementary data ( H and C NMR spectra of all
2
41.
16. Kumar, A.; Narayanan, R.; Shechter, H. J. Org. Chem.
996, 61, 4462.
1
1
7. Typical procedure for the synthesis of 1-(4-isopropylphen-
yl)-1H-1,2,3,4-tetrazole (5): A mixture of 4-isopropylani-
line (1 mmol), triethyl orthoformate (1.2 mmol), and
References and notes
1
. Butler, R. N. In Comprehensive Heterocyclic Chemistry;
Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds.;
Pergamon: Oxford, UK, 1996; Vol. 4.
sodium azide (1 mmol) in [Hbim]BF (3 mmol) was stirred
4
at 100 °C. The progress of the reaction was monitored by
TLC (EtOAc–petroleum ether, 7:13). After completion,
the reaction mixture was extracted with a mixture of ethyl
acetate–petroleum ether (4:6). The substituted tetrazole
extracts into the organic layer leaving behind the ionic
liquid as an immiscible phase. The organic layer was
separated, dried over sodium sulfate, and the solvent was
distilled off under reduced pressure. The isolated product
was pure (single spot on TLC) for all practical purposes. It
was subjected to further purification by column chroma-
tography (silica gel; EtOAc–petroleum ether, 1:3) to yield
the desired 1-(4-isopropylphenyl)-1H-1,2,3,4-tetrazole 5 in
an excellent yield of 90%. White solid; mp 68–69 °C; IR
2
3
4
. Singh, H.; Chawla, A. S.; Kapoor, V. K.; Paul, D.;
Malhotra, R. K. Prog. Med. Chem. 1980, 17, 151.
. Brown, M. U.S. Patent 3,338,915, 1967; Chem. Abstr.
1968, 87299.
. (a) Ostrovskii, V. A.; Pevzner, M. S.; Kofmna, T. P.;
Shcherbinin, M. B.; Tselinskii, I. V. Targets Heterocycl.
Syst. 1999, 3, 467; (b) Hiskey, M.; Chavez, D. E.; Naud,
D. L.; Son, S. F.; Berghout, H. L.; Bome, C. A. Proc. Int.
Pyrotech. Semin. 2000, 27, 3.
5
. (a) Burger, A. Prog. Drug Res. 1991, 37, 287; (b) Schelenz,
T.; Schafer, W. J. Fuel Prakt. Chem. 2000, 342, 91; (c)
Ruelke, H.; Friedel, A.; Martin, E.; Kottke, K.; Graefe, I.;
Kuehmstedt, H. Pharmazie 1991, 46.
(CHCl ): 2930, 2872, 1653, 1520, 1464, 1215, 1092, 1038,
3
À1
1
998 cm ; H NMR (200 MHz, CDCl ): d 1.29–1.33 (d,
3
6
. (a) Zimmerman, D. M.; Olofson, R. A. Tetrahedron Lett.
J = 6.95 Hz, 6H), 2.95–3.09 (m, 1H), 7.42–7.46 (d,
1
969, 58, 5081; (b) Fallon, F. G.; Herbst, R. M. J. Org.
J = 8.49 Hz, 2H), 7.60–7.64 (d, J = 8.70 Hz, 2H), 8.97 (s,
1H); C NMR (50 MHz, CDCl ): d 23.69, 33.78, 121.16,
3
128.03, 131.50, 140.51, 151.17; Anal. Calcd for C10H N :
12 4
1
3
Chem. 1957, 22, 933.
. Jin, T.; Kamijo, S.; Yamamoto, Y. Tetrahedron Lett. 2004,
7
4
5, 9435.
C, 63.81; H, 6.43; N, 29.77. Found: C, 63.97; H, 6.29; N,
29.68; LC–MS: 189.01.
8
. (a) Satoh, Y.; Marcopulos, N. Tetrahedron Lett. 1995, 36,
1759; (b) Gupta, A. K.; Oh, C. H. Tetrahedron Lett. 2004,
The ionic liquid, 1-n-butylimidazolium tetrafluoroborate
4
5, 4113.
([Hbim]BF
by us,
4
), was synthesized as per the method reported
and was successfully recycled and reused three
times without any considerable loss in yield.
1
2a
9
. Su, W.; Hong, Z.; Shan, W.; Zhang, X. Eur. J. Org. Chem.
006, 2733.
2