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Several 1(4-substituted)phenyl-4- or 5-methoxycarbonyl-1,2,3-triazoles have been synthesized by 1,3-dipolar cycloaddition of the corresponding arylazides to methyl propiolate in carbon tetrachloride. The regioselectivity of these reactions cannot be rationalized on the basis of the electronic demands of the reactants or frontier molecular-orbital theory. Therefore, we applied to this problem a quantitative formulation of the HSAB principle to this problem developed within density functional theory. Global and local reactivity indices were computed at B3LYP/6-311+G(d,p) level both in vacuo and in carbon tetrachloride (by the COSMO approach). The direction of charge transfer upon reactive encounter has been determined and the computed regioselectivity has been shown to be in good agreement with the experimental results. The relationship between computed and experimental data and how it is affected by the solvent have been discussed.

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Nitrilimine cycloadditions onto a variety of alkenyl dipolarophiles were performed for the first time in aqueous media. The observed cycloaddition outcome was markedly dependent on several factors, including the electronic features and the solubility in water of the dipolarophiles, as well as the presence of a cationic surfactant or an organic cosolvent in the reaction mixture.

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