On the utility of the azido transfer protocol: synthesis of 2- and 5-azido N-methylimidazoles, 1,3-thiazoles and N-methylpyrazole and their conversion to triazole–azole bisheteroaryls

Photoreactivity of monofluorinated 2-azidobenzimidazoles towards carboxylic acids

Aiming at the development of new photolabeling agents, the synthesis and photoreactivity of all monofluorinated derivatives of 2-azido-1-methylbenzimidazole are described. In the case of 4-, 5-, or 7-fluorination, irradiation in the presence of carboxylic acids (300 nm, Rayonet) afforded the monofluorinated 2-amino-6-acyloxybenzimidazoles in a regioselective manner, presumably after conversion of the initially formed nitrene to the N-cyanodiazaxylylene. Incorporation of chloride was also possible, and yields were comparable to those observed for the non-fluorinated parent compound. When blocking the reactive 6-position by a fluoro substituent, the title reaction was not possible. The analysis of the 19F NMR chemical shifts of the 5- and 7-monofluorinated products allowed the distinction between carboxylates and other nucleophiles.

Synthesis and reactions of 2-azido-1,3-di(benzyloxy)imidazolium hexafluoridophosphate

2-Azido-1,3-di(benzyloxy)imidazolium hexafluoridophosphate was obtained from the corresponding 2-bromo compound by reaction with sodium azide. Cycloaddition of the 2-azido compound with norbornene and norbornadiene gave the respective tricyclic aziridine and bicyclic azaoctadiene. Addition of triphenylphosphane yielded the phosphazide which upon heating eliminated dinitrogen to afford the phosphazene. The crystal structures of five compounds were determined by X-ray diffraction.

Crystal structure of 1-(1-methyl-1H-imidazol-2-yl)-4-phenyl-1H-1,2,3-triazole dihydrate

The title compound, C12H11N5·2H2O, which crystallizes as a dihydrate, was obtained by Cu(I)-catalysed azide-alkyne cyclo-addition from 2-azido-1-methyl-imidazole and phenyl-ethyne. The dihedral angles between the central triazole ring (r.m.s. deviation = 0.004 Å) and the pendant imidazole (r.m.s. deviation = 0.006 Å) and phenyl rings are 12.3 (2) and 2.54 (19)°, respectively. In the crystal, the water mol-ecules are connected into [010] chains by O-H⋯O hydrogen bonds, while O-H⋯N hydrogen bonds connect the water mol-ecules to the organic mol-ecules, generating corrugated (100) sheets.

Triazolbenzo[d]thiazoles: efficient synthesis and biological evaluation as neuroprotective agents

A number of (1H-1,2,3-triazol-1-yl)benzo[d]thiazoles were synthesized utilizing a versatile Cu-catalyzed azide-alkyne click reaction (CuAAC) on tautomeric benzo[4,5]thiazolo[3,2-d]tetrazole (1) and 2-azidobenzo[d]thiazole (2) starting materials. Moreover, one of the resulting products of this investigation, triazolbenzo[d]thiazole 22, was found to possess significant neuroprotective activity in human neuroblastoma (SH-SY5Y) cells.