Artículos de revistas
Conformational and electronic interaction studies of alpha-substituted carbonyl compounds. XV. alpha-(arylsulfinyl)-p-substituted acetophenones
Registro en:
Phosphorus Sulfur And Silicon And The Related Elements. Gordon Breach Sci Publ Ltd, v. 156, n. 255, n. 277, 2000.
1042-6507
WOS:000088788600020
10.1080/10426500008045008
Autor
Olivato, PR
Guerrero, SA
Rittner, R
Institución
Resumen
The V-CO IR analysis of alpha-(p-phenylsulfinyl)-p-substituted acetophenones X-phi C(O)CH2S(O) phi-Y 1-8, being X and Y = NO2, H and OMe substituents, supported by ab initio calculations of the alpha-methylsulfinyl/acetophenone (model compound) along with the X-ray geometrical data for 1, 7 and 8, indicates the existence of the cis(2) and gauche rotamers for compounds 1-4 and 6. Compounds 5, 7 and 8 present another less stable and more polar cis(1) rotamer. The cis(2) rotamer concentration for 4 (ca. 97% in CCl4) is reduced to ca. 50% for 2, 3, 5-7 and to ca. 20% for 1 and 8. This behavior is discussed in terms of O-(CO)(delta-)-S-(SO)(delta+) charge transfer and Coulombic interactions, which stabilize the cis(1) rotamer, and the pi(CO)/sigma*(C-S), pi*(CO)/n(s) and pi*(CO)/sigma(C-S) orbital interactions, which stabilize the gauche rotamers. The progressive more negative carbonyl cis(2) shifts (Delta v(c)), when X varies from NO2 to H and to OMe for the same Y, along with the unexpected NAE values of the alpha-methylene carbon chemical shifts for compounds 1-8 give further support for the existence of a strong intramolecular complex between C=O and S=O dipoles which stabilizes the cis(2) rotamer. The progressive more negative carbonyl gauche shifts (Delta v(g)), when X varies from NO2 to H and to OMe for the same Y, is in line with the higher contribution of the interaction pi(CO)/sigma*(C-S), which stabilizes the gauche rotamer of the title compounds. 156 255 277