Comparison of Conformations of Diesters of Stabilized Phosphonium Ylides in Solution and in the Crystal

Castañeda F.; Silva P.; Garland, MT; Shirazi, A; Bunton, CA

Abstract

Computed bond lengths and angles of methyl ethyl and dimethyl triphenyl phosphonium ylidic diesters, 1b, c, respectively, are similar to those in the crystal, as for the diethyl ester, 1a, where both acyl oxygens are anti to phosphorus. The 1H and 13C NMR spectra of the methyl ethyl diester, 1b, where one acyl oxygen is syn and the other anti to phosphorus, are as expected in terms of the conformation in the crystal, but the dimethyl ester, 1c, in the crystal is an equimolar mixture of conformers. For a given ylidic diester the different conformers have similar energies from B3LYP//6-31G(d) computations, interconversions of conformers should not be slow at ambient temperatures and 1H and 13C NMR signals in solution are sharp. Estimation of Natural Atomic Charges indicates significant cationoid character on phosphorus and the acyl carbons, and anionoid character on the ylidic carbon and the ester oxygens depending on orientations towards phosphorus.

Más información

Título según WOS: Comparison of Conformations of Diesters of Stabilized Phosphonium Ylides in Solution and in the Crystal
Título según SCOPUS: Comparison of conformations of diesters of stabilized phosphonium ylides in solution and in the crystal
Título de la Revista: PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS
Volumen: 184
Número: 1
Editorial: GORDON BREACH SCI PUBL LTD
Fecha de publicación: 2009
Página de inicio: 19
Página final: 33
Idioma: English
URL: http://www.scopus.com/inward/record.url?eid=2-s2.0-58049173668&partnerID=q2rCbXpz
DOI:

10.1080/10426500802077242

Notas: ISI, SCOPUS