Categories: Synthesis of N-Heterocycles >
Synthesis of tetrazoles
Treatment of organic nitriles with NaN3 in the presence of iodine or silica-supported sodium hydrogen sulfate as a heterogeneous catalyst enables an advantageous synthesis of 5-substituted 1H-tetrazoles.
B. Das, C. R. Reddy, D. N. Kumar, M. Krishnaiah, R. Narender, Synlett, 2010, 391-394.
5-Substituted tetrazoles were prepared in very good yields and short reaction times by treatment of nitriles with sodium azide and triethylammonium chloride in nitrobenzene in a microwave reactor. Even sterically hindered tetrazoles, as well as those deactivated by electron-donating groups, can be prepared.
J. Roh, T. V. Artamonova, K. Vávrová, G. I. Koldobskii, A. Hrabálek, Synthesis, 2009, 2175-2178.
An organocatalyst, 5-azido-1-methyl-3,4-dihydro-2H-pyrrolium azide, generated in situ from N-methyl-2-pyrrolidone (NMP), sodium azide, and trimethylsilyl chloride, enables the formation of tetrazoles by cycloaddition of sodium azide with organic nitriles under neutral conditions and microwave heating. The organocatalyst accelerates the azide-nitrile coupling by activating the nitrile substrate.
D. Cantillo, B. Gutmann, C. O. Kappe, J. Am. Chem. Soc., 2011, 133, 4465-4475.
A series of 1-substituted 1H-1,2,3,4-tetrazole compounds have been synthesized in good yields from amines, triethyl orthoformate, and sodium azide through the catalyzed reaction with Yb(OTf)3.
W.-K. Su, Z. Hong, W.-G. Shan, X.-X. Zhang, Eur. J. Org. Chem., 2006, 2723-2726.
A series of primary alcohols and aldehydes were treated with iodine in ammonia water under microwave irradiation to give the intermediate nitriles, which without isolation underwent [2 + 3] cycloadditions with dicyandiamide and sodium azide to afford the corresponding triazines and tetrazoles in high yields.
J.-J. Shie, J.-M. Fang, J. Org. Chem., 2007, 72, 3141-3144.
Cascade reactions starting from isocyanides allow a straightforward synthesis of five-membered ring heterocycles. Addition of sodium azide on isocyanide dibromides followed by electrocyclization and a Suzuki coupling affords tetrazoles scaffolds, whereas addition of tetrazoles on isocyanide dibromides followed by Huisgen rearrangement and a Suzuki coupling gives triazoles scaffolds.
L. El Kaim, L. Grimaud, P. Patil, Org. Lett., 2011, 13, 1261-1263.
A general method for the synthesis of 1,5-disubstituted tetrazoles from imidoylbenzotriazoles involves mild reaction conditions and short reaction times.
A. R. Katritzky, C. Cai, N. K. Meher, Synthesis, 2007, 1204-1208.
The reaction of cyanogen azide and primary amines generates imidoyl azides as intermediates in acetonitrile/water. After cyclization, these intermediates gave 1-substituted aminotetrazoles in good yield.
Y.-H. Joo, J. M. Shreeve, Org. Lett., 2008, 10, 4665-4667.
A versatile and highly efficient Zn(OTf)2-catalyzed one-pot reaction of alkenes, NBS, nitriles, and TMSN3 gives various 1,5-disubstituted tetrazoles containing an additional α-bromo functionality of the N1-alkyl substituent.
S. Hajra, D. Sinha, M. Bhowmick, J. Org. Chem., 2007, 72, 1852-1855.
The reaction of 2-halopyridines with trimethylsilyl azide in the presence of tetrabutylammonium fluoride hydrate gives tetrazolo[1,5-a]pyridines. 8-bromotetrazolo[1,5-a]pyridine is further transformed into a variety of novel tetrazolo[1,5-a]pyridine derivatives.
J. K. Laha, G. D. Cuny, Synthesis, 2008, 4002-4006.
Pyridine N-oxides were converted to tetrazolo[1,5-a]pyridines in good yield in the presence of sulfonyl or phosphoryl azides and pyridine by heating in the absence of solvent. Diphenyl phosphorazidate (DPPA) was the most convenient reagent.
J. M. Keith, J. Org. Chem., 2006, 71, 9540-9543.