Studies on the reactivity of derivatives of tetrazole and isothiazole; isothiazolyltetrazoles as potential bidentate ligands and their application in catalysis

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Synthesis and structure of novel benzisothiazole-tetrazolyl derivatives for potential application as nitrogen ligands

Publication . Frija, L.; Fausto, R.; Loureiro, Rui M. S.; Cristiano, Maria Lurdes Santos

The synthesis and characterization of novel benzisothiazole-tetrazolyl derivatives differing on the spacer-group used for the linkage of two heterocycles are described. The application of these compounds as nitrogen ligands for coordination with transition metals was also explored, leading to the preparation of 3-[1-(2-1H-tetrazol-5-yl)ethoxy]-1,2-benzisothiazole 1,1-dioxide-Mn(II) and N-(1,1-dioxo-1,2-benzisothiazol-3-yl)-amine-1H-tetrazole-Mn(II) complexes.

2009Journal article

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Photochemistry of 5-allyloxy-tetrazoles: steady-state and laser flash photolysis study

Publication . Frija, L.; Khmelinskii, Igor; Serpa, C.; Reva, I. D.; Fausto, R.; Cristiano, Maria Lurdes Santos

The photochemistry of three 5-allyloxy-tetrazoles, in methanol, acetonitrile and cyclohexane was studied by product analysis and laser flash photolysis. The exclusive primary photochemical process identified was molecular nitrogen elimination, with formation of 1,3-oxazines. These compounds were isolated in reasonable yields by column chromatography on silica gel and were fully characterized. DFT(B3LYP)/6-31G(d,p)calculations predict that these 1,3-oxazines can adopt two tautomeric forms (i) with the NH group acting as a bridge connecting the oxazine and phenyl rings and (ii) with the –N=bridge and the proton shifted to the oxazine ring. Both tautomeric forms are relevant in the photolysis of oxazines in solution. Secondary reactions were observed, leading to the production of phenyl vinyl-hydrazines, enamines, aniline and phenyl-isocyanate. Transient absorption, detected by laser flash photolysis, is attributed to the formation of triplet 1,3-biradicals generated from the excited 5-allyloxy-tetrazoles. The 1,3-biradicals are converted to 1,6-biradicals by proton transfer, which, after intersystem crossing, decay to generate the products. Solvent effects on the photoproduct distribution and rate of decomposition are negligible.

2008Journal article

Open Access