Tetrazoles and ring-fused derivatives

3-Diaryltetrazole-5-thiones were prepared and theoretical studies on atomic charge distributions were performed on these compounds 05JOC8322 . 

5-Pyrrolidin-2-yltetrazole 204 has been found to be a new, catalytic, and more soluble alternative to proline in a highly selective, organocatalytic route to chiral dihydro-1,2-oxazines 05OL4189 and as an asymmetric organocatalyst for Mannich, nitro-Michael and aldol 

Hanamoto, Y. Koga, E. Kido, T. Kawanami, H. Furuno, J. Inanaga, J. Chem. Soc., Chem. Commun. 2005, 2041. 

Gonzalez-Nogal, M. Calle, L.A. Calvo, P. Cuadrado, A. Gonzalez-Ortega, Eur. J. Org. Chem. 2005, 4663. 

Buscemi, A. Pace, A.P. Piooionello, 1. Pibiri, N. Vivona, Heterocycles 2005, 65,387. 

A review has been published on the methods of functionalization of tetrazoles for the period 2001 to mid 2005 06RJOC469 . The search for new radical structures having both low selectivity and high reactivity toward the addition reaction onto alkenes has led to a new tetrazole-derived thiyl radical 06JOC9723 . 

Pyridine A-oxides were converted to tetrazolo[l,5-a]pyridines 172 by heating in the presence sulfonyl or phosphoryl azides and pyridine in the absence of solvent 06JOC9540 . 3-R-5-Trinitromethyltetrazolo[l,5-a]-l,3,5-triazin-7-ones 173 have been prepared from the alkylation of 5-trinitromethyltetrazolo[l,5-a]-l,3,5-triazin-7-one silver salt with different alkylation agents 06CHE417 . The use of 2-fluorophenylisocyanide in the combinatorial Ugi-tetrazole reaction followed by a nucleophilic aromatic substitution afforded tricylic tetrazolo[l,5-a]quinoxaline 174 in good yields and with high diversity 06TL2041 . 

Bouabdallah, R. Touzani, I. Zidane, A. Ramdani, S. Radi, Arkivoc, 2006,14, 46. 

Kuleshov, K.Y. Borovkov, O.G. Rodin, V.P. Perevalov, Heterocycl Compd. (Engl. Transl.) 2006,42, 246. 

A review of drugs in the tetrazole series was published 07CHC1 . 

R = PhS02, BnS, 2-pyrrolidinyl, C02Et, cyclohexenyl, styryl, Ar, pyridinyl, 2-furanyl, 2-thiophenyl 

A solid-phase supported synthesis of substituted /V-terminal 5-aminotetrazole peptides via electrocyclization of peptidic imidoylazides has been reported 07JCO644 . 

Katritzky, A.V. Vakulenko, R. Akue-Gedu, A.V. Gromova, R. Witek, J.W. Rogers,Arkivoc (Archives for Organic Chemistry) 2007,1, 9. 

Al-Matar, S.M. Riyadh, M.H. Elnagdi, Arkivoc (Archives for Organic 

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Synthesis of Tetrazoles and Ring-Fused Derivatives via Nitrogenation Strategy... 

A Hungarian research group observed a nonexpected formation of a tetrazolo[l,5- ]derivative <2001J(P 1) 1131 >. These authors found that treatment of the /3-lactam-substituted tetrazolylmethyl ketone 135 with lead tetraacetate results in a ring closure to pyridine ring fused to tetrazole, and product 136 was formed as a mixture of diastereomers in low yield (Scheme 33). 

Several ring-fused tetrazole compounds have been reported. 2-Methyl-3-cyanopyridines were converted into their corresponding 2-azidomethyl derivatives, which underwent intramolecular cycloaddition reactions to give 3-(tetrazol-5-yl)pyridines 186 <04TL9127>. Fused tetrazole derivatives 187 were obtained via tandem cycloaddition and yV-allylation reactions <04JOC1346>. Expeditive synthesis of homochiral fused tetrazole piperazines 188 from 3-amino alcohols has been reported <04TL3725>. A novel Ugi-five-center-four-component reaction (U-5C-4CR) of aldehydes, primary amines, trimethylsilyl azide and 2-isocyanoethyl tosylate afforded tetrazolopiperazine type compounds <04TL6421>. 

An alternative approach to 5-5 bicyclic fused ring systems utilizing a condensation reaction was described by Moderhack et al. <2000JPC591> (Scheme 10). The amino-substituted tetrazole derivatives 52 and 54 gave the neutral 53 as well as the mesoionic derivatives 55 in moderate to excellent yields (16-86% R = CH3 or Ph). 

Extension of these studies to benzologues of tetrazolo[l,5- ]pyridine, that is, for tetrazolo[l,5- ]quinoline 21 and tetrazolo[5,l- ]isoquinoline 22, led to interesting results <2003JOC1470> as shown in Scheme 7. Both of these fused tetrazoles resulted in formation of a nitrene 23 and 24, respectively, which could be interconverted via formation of the fused cyclic carbodiimide derivative 25. Isoquinolylnitrene 24, furthermore, was found to undergo subsequent reactions ring opening afforded the vinylnitrene 26, which was transformed to o-cyanophe-nylacetonitrile 27 by a 1,2-H shift and to 4-cyanoindole 28 by an intramolecular cyclization in 40% and 25% yields, respectively. 

The fused tetrazole 422 (Scheme 19) was originally assumed307" to be nitrated on the thiazole ring, but recent NMR studies have shown that a p-nitrophenyl derivative is formed.1836 Since 422 (and 424) display azide tetrazole tautomerism (Section IV,B,1), the exact structure of the reacting species is unknown, but the product exists predominantly as the azide. 

Chi the basis of the tautomeric formulas shown for 5-monosubstituted tetrazoles (where R is any substituent) there are three classes of monosub stituted and two classes of disubstituted derivatives (where the H is replaced). Also, there are fused ring tetrazoles of the 1,5-disub stituted class. In addn, there are salts and substituted derivatives which have 2,3-, 1,4- and 1,2-sub-stituents. However, compds of ordn interest are usually 1,5-, 2,5- or 1,3-substituted. Bis expl compds may be connected at the 5,5 -positions. Bis expl salts may be connected at either the 1,1 or the 5,5position with the (metallic) anion. (See in Vol 2, B157-L R and below under the pertinent compds)... 

Scott and others have shown that the hydrazones of many azoles undergo ring closure to fused triazoles [Eq. 20)] either by oxidation (R = H) or by displacement of halogen (R = Br). Thus triazolotriazoles (180) were obtained by lead tetraacetate oxidation of the corresponding s-triazolehydrazone, " or by displacement of bromine from the appropriate bromo derivative. s-Triazolo[4,3-rf]tetrazoles (181) were prepared by oxidation or displacement of bromine " from the appropriate derivative, and similar methods were used to prepare s-triazolobenzothiazoles (182) s-triazolooxadiazoles (183), and pyrazolo[3,2-c]-s-triazoles. ... 

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