- Dual Reactivity of 1,2,3,4-Tetrazole: Manganese-Catalyzed Click Reaction and Denitrogenative Annulation
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A general catalytic method using a Mn-porphyrin-based catalytic system is reported that enables two different reactions (click reaction and denitrogenative annulation) and affords two different classes of nitrogen heterocycles, 1,5-disubstituted 1,2,3-triazoles (with a pyridyl motif) and 1,2,4-triazolo-pyridines. Mechanistic investigations suggest that although the click reaction likely proceeds through an ionic mechanism, which is different from the traditional click reaction, the denitrogenative annulation reaction likely proceeds via an electrophilic metallonitrene intermediate rather than a metalloradical intermediate. Collectively, this method is highly efficient and offers several advantages over other methods. For example, this method excludes a multi-step synthesis of the N-heterocyclic molecules described and produces only environmentally benign N2 gas a by-product.
- Chattopadhyay, Buddhadeb,Das, Sandip Kumar,Khatua, Hillol,Roy, Satyajit
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supporting information
p. 304 - 312
(2020/10/29)
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- Iron(II)-Based Metalloradical Activation: Switch from Traditional Click Chemistry to Denitrogenative Annulation
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A unique concept for the intermolecular denitrogenative annulation of 1,2,3,4-tetrazoles and alkynes was discovered by using a catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradical activation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates.
- Roy, Satyajit,Khatua, Hillol,Das, Sandip Kumar,Chattopadhyay, Buddhadeb
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supporting information
p. 11439 - 11443
(2019/07/17)
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- Synthesis of tetrazolo[1,5-a]pyridines utilizing trimethylsilyl azide and tetrabutylammonium fluoride hydrate
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A method for the preparation of tetrazolo[1,5-a]pyridines from 2-halopyridines, utilizing trimethylsilyl azide in the presence of tetrabutylammonium fluoride hydrate, is described. In addition, 8-bromotetrazolo[1,5-a]pyridine is further transformed into a variety of novel tetrazolo[1,5-a]pyridine derivatives. Georg Thieme Verlag Stuttgart.
- Laha, Joydev K.,Cuny, Gregory D.
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experimental part
p. 4002 - 4006
(2009/05/27)
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- 1H, 13C and 15N NMR and IR studies of halogen-substituted tetrazolo[1,5-a]pyridines
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The tetrazole-azide tautomerization of some halogen-substituted tetrazolo[1,5-a]pyridines was examined by IR spectroscopy at ambient temperature and by 1H, 13C and 15N NMR spectroscopy at various temperatures. The tetrazolopyridines can exhibit equilibrium between the azide and the tetrazole forms. For some of them slow exchange occurs on the NMR time-scale, such that it is possible to estimate equilibrium constants. The position and nature of the substituent in the pyridine ring result in stabilization or destabilization of the tetrazole form and exert a strong influence on the values found for the equilibrium constants. A saturation transfer experiment was carried out for 5-bromotetrazolo[1,5-a]pyridine and the rate constants were estimated. Moreover, based on the van't Hoff equation, the enthalpy ΔHo and entropy ΔSo for the tautomerization were calculated. Ab initio calculated energies and charge distribution are in good agreement with differences observed in the tetrazole-azide equilibrium constants. Copyright
- Cmoch,Korczak,Stefaniak,Webb
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p. 470 - 478
(2007/10/03)
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- NMR studies of the equilibria produced by 6- and 8-substituted tetrazolo [1,5-a] pyridines
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1H, 13C and 15N NMR data are reported for nine tetrazoles. Five of these compounds are found to exhibit valence tautomeric equilibrium between the tetrazole and azide forms. The position of this equilibrium at 298 K is found to be dependent on the solvent and the position and nature of the substituent. More polar solvents favour the tetrazole form. Protonation studies on the two forms using TFA as a solvent are reported. The favoured site of protonation is found to be N-4 for the azide form and N-1 for the tetrazole form.
- Cmoch, Piotr,Stefaniak, Lech,Webb, Graham A.
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p. 237 - 242
(2007/10/03)
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