Tetrazole compounds

Abstract In this chapter, selected results obtained so far on Fe(II) spin crossover compounds of 1,2,4-triazole, isoxazole and tetrazole derivatives are summarized and analysed. These materials include the only compounds known to have Fe(II)N6 spin crossover chromophores consisting of six chemically identical heterocyclic ligands. Particular attention is paid to the coordination modes for substituted 1,2,4-triazole derivatives towards Fe(II) resulting in polynuclear and mononuclear compounds exhibiting Fe(II) spin transitions. Furthermore, the physical properties of mononuclear Fe(II) isoxazole and 1-alkyl-tetrazole compounds are discussed in relation to their structures. It will also be shown that the use of a,p- and a,C0-bis(tetrazol-l-yl)alkane type ligands allowed a novel strategy towards obtaining polynuclear Fe(II) spin crossover materials. 

The same authors found quite recently that the tetrazole compound 11 when reacted with 1,2-dihydrobenzene, the monocycloadduct 50 as a racemate is formed in high yield (84%) <2005TL8363>. 

Because of the presence of two azide groups in positions adjacent to the ring nitrogen atoms in compound 13a, valence bond isomerization can result in formation of 6-azido-7-methyltetrazolo[l,5-A pyridazine 14a, 6-azido-8-methyltetrazolo[l,5-A pyridazine 15a, and the bis-tetrazole compound 16a. Calculations have been carried out by using hybrid density functional theory (B3LYP/6-311+G(d,p)) and complete basis set treatments (CBS-4M). All calculations revealed that the 8-methyl derivative 15a is the most stable isomer. Similar studies on the triazide derivative 13b, however, indicated that in this case the equilibrium is shifted to the 7-methyl form 14b. All these conclusions proved to be in entire agreement with the experimental findings (see Section 11.18.3.2.). 

Ring opening of the five-membered tetrazole ring has also been observed in several cases. The most trivial conversion is the equilibrium between the fused tetrazole and azidodiazine which, in principle, could take place with every fused tetrazole compound described in this chapter, and, therefore, no special comment on this type of ring opening needs to be discussed. 

CA 46, 4350 (1952) [The AHC of 5-Nitro-aminotetrazole is reported as 222.6Kcal/mole] 3a) W.F. Sager D.V. Sickman, Research and Development in New Chemical High Explosives , NAVORD 483 (1952) [Addnl properties of 5-ATZ Nitrate reported are a cryst d of 1.82 g/cc and an impact sensy approaching that of Pentolite] 3b) J.H. Bryden, The Unit-Cell Dimensions and Space Groups of Some Tetrazole Compounds , ActaCryst 6, 669—70 (1953) CA 47, 10947 (1953) [Table 1, below, delineates these properties ... 

Unit Cell Dimensions and Space Groups of Some Amino-Tetrazole Compounds (Ref 3b)... 

Tetrazole compounds are also good starting materials for the synthesis of energetic materials with substituted side-chains attached to the tetrazole skeleton. For... 

Out of the different possible derivatives of tetrazoles, we have so far only discussed (A) and nitriminotetrazole (D) (Fig. 9.14) in more detail. Although the azide-substituted tetrazole compound of type C is very energetic, it is still not useful for practical application since it is extremely sensitive. Additionally of interest are the neutral and ionic nitrotetrazole derivates of type F, which are more stable (Fig. 9.14). 

A very interesting approach to the synthesis of new, ethyl-bridged, energetic tetrazole compounds, both neutral and ionic has been reported recently by Shreeve and co-workers [56a,b]. They react in situ generated cyanazide, N3CN, with 1,2-diaminoethane to form the bridged tetrazole derivative A (Fig. 9.17), which can sub-... 

Another very promising tetrazole compound, bistetrazolylamine (H2BTA), can be obtained directly from sodium dicyanamide and sodium azide [56c] ... 

FIGURE 8.8 Molecular structure of BTA and heterocyclic tetrazole compounds (ATA, PTA, and PTT). 

Mihit M, El Issami S, Bouklah M, Bazzi L, Hammouti B, Ait Addi E, Salghi R, Kertit S. The inhibited effect of some tetrazolic compounds towards the corrosion of brass in nitric acid solution. Appl Surf Sci 2006 252 2389. 

Young, A.M., Audus, KL., ProudfooL J., and Yazdanian, M. (2006) Tetrazole compounds the efiect of structure and pH on Caco-2 cell permeability. Journal of Pharmaceutical Sciences, 95, 717-725. 

Figure 1 UV-spectra during irradiation of a tetrazole (compound analogous to 2.7d, see page 142, 1.02 x 10" M in ethanol, mercury high-pressure lamp, pyrex lamp) from H. Meier, H. Heimgartner, Helv. Chim. Acta 1985, 68,1287.

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>. 

For every biologically active carboxylic acid, there is a bioisosteric compound in which the carboxyl group is replaced by a tetrazol-5-yl moiety. The tetrazole compounds are degraded biologically more slowly than carboxylic acids. For instance, the tetrazole analogue 11 of nicotinic acid reduces the fatty acid and cholesterol levels in blood. 

---