Chiral “basket handle” binaphthyl porphyrins: synthesis,catalytic epoxidation and NMR conformational studies
Articolo
Data di Pubblicazione:
2010
Citazione:
Chiral “basket handle” binaphthyl porphyrins: synthesis,catalytic epoxidation and NMR conformational studies / E. Rose, E. Gallo, N. Raoul, L. Bouché, A. Pille, A. Caselli, O. Lequin. - In: JOURNAL OF PORPHYRINS AND PHTHALOCYANINES. - ISSN 1088-4246. - 14:7(2010), pp. 646-659. [10.1142/S1088424610002483]
Abstract:
Three “basket handle” porphyrins have been prepared by condensation of tetrakis-(α,β,α,β-2-aminophenyl)porphyrin atropoisomer with 1,1′-binaphthyl, 2,2′-dimethoxy, -3,3′-dicarbonylchloride, -3,3′-diacetylchloride and -3,3′-dipropanoylchloride. The epoxidation of styrene with the three iron catalysts, obtained after metalation of the free porphyrins, occurs with good yields and moderate ee up to 54%. These porphyrins showed unexpected conformational differences, as revealed by NMR spectroscopy. In particular, variable temperature NMR studies showed that the methoxy group in one of them undergoes intermediate conformational exchange on the 1H NMR time scale at room temperature. Lowering the temperature to -50 °C revealed the presence of four states in slow exchange on the NMR time scale. These results evidence a dynamic conformational equilibrium of the binaphthyl handles that adopt different, asymmetric positions with respect to the porphyrin plane.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
chiral porphyrin; NMR; conformational exchange; binaphthyl porphyrin; enantioselective epoxidation
Elenco autori:
E. Rose, E. Gallo, N. Raoul, L. Bouché, A. Pille, A. Caselli, O. Lequin
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