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Sigmatropic rearrangements in 5-allyloxytetrazoles
Frija, L.; Reva, I. D.; Ismael, A.; Coelho, Daniela; Fausto, R.; Cristiano, Maria Lurdes SantosMechanisms of thermal isomerization of allyl tetrazolyl ethers derived from the carbocyclic allylic alcohols cyclohex-2-enol and 3-methylcyclohex-2-enol and from the natural terpene alcohol nerol were investigated. In the process of the syntheses of the three 1-aryl-5-allyloxytetrazoles, their rapid isomerization to the corresponding 1-aryl-4-allyltetrazol-5-ones occurred. The experiments showed that the imidat...
Photochemical Transformations of Tetrazole Derivatives: Applications in Organic...
Frija, L.; Ismael, A.; Cristiano, Maria Lurdes SantosTetrazoles remain a challenge to photochemists. Photolysis leads to cleavage of the tetrazolyl ring, may involve various photodegradation pathways and may produce a diversity of photoproducts, depending on the structure and conformational flexibility of the substituents and the possibility of tautomerism. If the photochemistry of tetrazoles is considered within the frame of synthetic applications the subject is...
Photochemistry of 5-allyloxy-tetrazoles: steady-state and laser flash photolysi...
Frija, L. M. T.; Khmelinskii, I. V.; Serpa, C.; Reva, I. D.; Fausto, R.; Cristiano, M. L. S.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...
Photochemistry of 5-allyloxy-tetrazoles: steady-state and laser flash photolysi...
Frija, L.; Khmelinskii, Igor; Serpa, C.; Reva, I. D.; Fausto, R.; Cristiano, Maria Lurdes SantosThe 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...
Investigation of structural effects on the reactivity of heterocyclic bioactive...
Frija, L.Tese de dout., Química, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2008 ; In the course of this investigation, structural effects on the reactivity of a series of heterocyclic compounds, in particular tetrazole and benzisothiazole derivatives, submitted to different chemical environments, were explored. The photochemistry of several representative tetrazoles was considered in solution and for...
UV-induced photochemistry of matrix-isolated 1-phenyl-4-allyl-tetrazolone
Frija, L. M. T.; Reva, I. D.; Gómez-Zavaglia, A.; Cristiano, M. L. S.; Fausto, R.The photochemistry and molecular structure of 1-phenyl-4-allyl-tetrazolone (PAT) was studied by FT-IR matrix isolation spectroscopy and DFT(B3LYP)/6-311++G(d,p) calculations. The spectrum of matrix-isolated PAT monomers agrees well with the sum spectrum of three conformers predicted theoretically. UV irradiation (λ > 235 nm) of matrix-isolated PAT induces three types of photofragmentation: (1) production of phe...
UV-induced photochemistry of matrix-isolated 1-phenyl-4-allyl-tetrazolone
Frija, L.; Reva, I. D.; Gómez-Zavaglia, A.; Cristiano, Maria Lurdes Santos; Fausto, R.The photochemistry and molecular structure of 1-phenyl-4-allyl-tetrazolone (PAT) was studied by FT-IR matrix isolation spectroscopy and DFT(B3LYP)/6-311++G(d,p) calculations. The spectrum of matrix-isolated PAT monomers agrees well with the sum spectrum of three conformers predicted theoretically. UV irradiation (k > 235 nm) of matrix-isolated PAT induces three types of photofragmentation: (1) production of phe...
Photochemistry of 1-phenyl-tetrazolone isolated in solid argon
Gómez-Zavaglia, A.; Reva, I.D.; Frija, L.; Cristiano, M.L.; Fausto, R.The molecular structure, vibrational spectra, tautomerism and photochemistry of the derivative of tetrazole, 1-phenyl-tetrazolone (C7H6N4O; PT) have been studied by FT-IR matrix isolation spectroscopy and DFT/B3LYP/6-311++G(d,p) calculations. Among the five structures in which PT could be expected to exist (two keto tautomers, one mesoionic olate-form and two different conformers of the hydroxyl tautomer), only...
Photochemical Ring-Opening and Intramolecular Hydrogen Shift Reactions in Sulfu...
Breda, S.; Reva, I.; Lapinski, L.; Cristiano, M. L. S.; Frija, L.; Fausto, R.A combined matrix isolation FTIR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the photochemistry of sulfur analogues of α-pyrone [2H-thiopyran-2-one (TP) and 2H-pyran-2-thione (PT)] was carried out. The vibrational spectra of monomers of the compounds isolated in low-temperature argon matrixes were studied experimentally and assigned completely on the basis of theoretical calculations. UV irradiation (λ > ...
Infrared spectrum and UV-induced photochemistry of matrix-isolated 5-methoxy-1-...
Gómez-Zavaglia, Andrea; Reva, I. D.; Frija, L.; Cristiano, M. L. S.; Fausto, R.The molecular structure, vibrational spectra and photochemistry of 5-methoxy-1-phenyl-1H-tetrazole (5MPT) were studied by matrix isolation infrared spectroscopy and DFT(B3LYP)/6-311++G(d,p) calculations. According to the calculations, only one double degenerated-by-symmetry minimum exists in the ground state PES of the compound. In this structure, the dihedral angle between the two rings (phenyl and tetrazole) ...
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