Mechanistic insights on the site selectivity in successive 1,3-dipolar cycloadditions to meso-tetraarylporphyrins |
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Authors: | G Jiménez-Osés JI García ARN Santos MGPMS Neves |
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Institution: | a Departamento de Química Orgánica, Instituto de Ciencia de Materiales de Aragón, Instituto Universitario de Catálisis Homogénea, Universidad de Zaragoza-CSIC, E-50009 Zaragoza, Spain b Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal |
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Abstract: | A DFT study on site selectivity in successive 1,3-dipolar cycloadditions of meso-tetraarylporphyrins with azomethine ylide and N-methylnitrone has been carried out. The calculation of the thermodynamic stability of both ylide and nitrone-derived adducts reveals that bacteriochlorins are more stable and have stronger aromatic character than isobacteriochlorins. Calculations of whole reaction pathways show that cycloadditions of azomethine ylide on porphyrin and its derived chlorin are irreversible and hence kinetically controlled. Solvent influence on the site selectivity of this reaction has also been considered, and appears to be decisive in controlling the site selectivity. In contrast, cycloadditions of nitrone over porphyrin and chlorin are clearly reversible, pointing to a thermodynamic control of these reactions. |
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Keywords: | Porphyrins Bacteriochlorins Isobacteriochlorins Site selectivity 1 3-Dipolar cycloadditions DFT calculations Solvent effects Aromaticity |
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