The compound, diethyl 1-((4-methyl-2-phenyl-4,5-dihydrooxazol-4-yl)methyl)-1H-1,2,3-triazole-4,5-dicarboxylate 2, was synthesized in high yield, through 1,3-dipolar cycloaddition reaction of 4-(azidomethyl)-4-methyl-2-phenyl-4,5-dihydrooxazole and diethyl but-2-ynedioate in the absence of a solvent. The structure of the synthesized compound was established on the basis of NMR spectroscopy ( 1 H, 13 C), X-ray crystallography, and MS data. The prepared compound was also tested in vitro for its antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). The calculation of MBC/MIC ratio showed that this triazole derivative 2 had a bactericidal effect on the two strains tested.

The biheterocyclic derivative of the phosphonic glycine analogue is prepared selectively by reaction between the α-azidoamino diethyl methylphosphonate and the 1-(prop-2-yn-1-yl)-1H-benzo[d]imidazole. The dipolar -1,3 cycloaddition reaction using Click Chemistry was carried out in a solvent water/ethanol mixture in a ratio of 1:1. Copper sulphate pentahydrate and sodium ascorbate are used in the reaction in catalytic amounts. The compound [diethyl [{4-[(1H-benzo[d]imidazol-1-yl)methyl]-1H-1,2,3-triazol-1-yl}(benzamido) methyl] phosphonate was isolated pure as a white powder, after chromatography on a silica gel column (ethyl acetate/hexane acetate: 1/1). The yield of pure product is 90%, after recrystallization in an ether/hexane mixture. The structure of the -1,4 isomer is attributed to the compound obtained by means of 1D and 2D NMR and based on data from the literature concerning the cycloaddition reaction via Click Chemistry. Two-dimensional NMR spectroscopy played a major role. The analysis of the different correlations between adjacent hydrogens and carbons, and also between hydrogens and distant carbons, confirmed the proposed structure.

In the title compound, C28H29N5O, the molecule adopts an approximate U-shape, a conformation imposed at least in part by an intramolecular π–π contact between the two five-membered rings, which display a centroid-to-centroid separation of 3.6522 (7) Å. The planes of these rings are inclined to one another by 66.12 (5)°. A weak intramolecular C—H...·N hydrogen bond is also found. The planes of the phenyl rings of the amine unit are inclined at a dihedral angle of 81.10 (4)°, while that of the 4,5-dihydrooxazole ring makes an angle of 11.74 (8)° with its phenyl substituent. The crystal packing is stabilized by C—H...N hydrogen bonds that form chains parallel to thebaxis. Several C—H...π(ring) contacts are also present.

The identity of the 2-(4-Methyl-2-phenyl-4,5-dihydrooxazol-4-ylmethyl)-isoindole-1,3-dione, previously synthesized in our laboratory, was proven without doubt by means of 1D and 2D NMR spectroscopy. Two-dimensional NMR spectroscopy played a major role. The analysis of the 2D-COSY spectrum of isoindoline-1,3-dione derivative shows a perfect correlation between neighboring protons. Thus, a correlation was noted between the protons of the phthalimide, H(8) and H(9) on the one hand and H(8') and H(9') on the other hand. The analysis of the 2D-HSQC spectrum of the studied compound indicates a faultless correlation between protons and adjacent carbons, and no correlation in the case of all quaternary carbons.

In this paper, we describe the regioselective synthesis of a novel tri-heterocyclic compound, a biheterocyclic amino acid precursor, derived from both triazole and tetrazole. The key step of our synthesis approach was the Huigsen 1,3-dipolar cycloaddition reaction, catalyzed by the copper (I) formed in situ by reduction of Cu(II) salts (CuSO4), 5H2O) by sodium ascorbate, and using as dipole the oxazoline azide derivative 4-(azidomethyl)-4-ethyl-2-phenyl-4,5-dihydrooxazole (4) and as dipolarophile 5-(4-methoxyphenyl)-2-(prop-2-yn-1-yl)-2H-tetrazole (3).  The Cu(I) catalysis allowed us to carry out the cycloaddition at room temperature during a reaction time of only 8 hours and also to selectively obtain the 1,4-regioisomer; one of the two possible isomers, with a yield of 90% after chromatography on a silica gel column (ether/hexane: 1/2), and recrystallization in an ether/acetone mixture. The desired compound, 4-ethyl-4-((4-((5-(4-methoxyphenyl)-2H-tetrazol-2-yl)methyl)-1H-1,2,3-triazol-1-yl)methyl)-2-phenyl-4,5-dihydrooxazole (5) was analyzed by 1D magnetic resonance spectroscopy (1H, 13C), and characterized physico-chemically by mass spectrometry and elemental analysis.