Conformational analysis of p-X-anilino dioxaphosphinanes. Substituent effects on 31P and 15N NMR signals and on negative hyperconjugation (n–σ)

• Published in: Tetrahedron Vol. 66; no. 11; pp. 2066 - 2076
• Main Authors: Domínguez, Zaira, Galván, Marcelo, Cortez, Ma. Teresa, Salas, Magali, Meza, Rocío, Leyva-Ramirez, Marco A., Gordillo, Barbara
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2010; Elsevier
• Subjects: Chemistry; Conformation; Dioxaphosphinanes; Exact sciences and technology; Heterocyclic compounds; Miscellaneous; Negative hyperconjugation; NMR; Noncondensed benzenic compounds; Organic chemistry; Organometalloidal and organometallic compounds; P derivatives; Preparations and properties; SCS and LFER correlations; Thiophosphoramidates; X-ray crystal structures; X-ray crystal structures; NMR; SCS and LFER correlations; Negative hyperconjugation; Thiophosphoramidates; Dioxaphosphinanes; Conformation; Substituent effect; Correlation; Nitrogen 15; Stabilization; Conformational analysis; Molecular interaction; NMR spectrometry; Oxygen phosphorus heterocycle; Organic sulfide; Steric effect; Phosphorus 31; Chemical solution; Theoretical study; Hyperconjugation; Coupling constant; Aniline derivatives; X ray diffraction; Chemical shift; Density functional method; Benzenic compound; Electronic effect; Diastereomer
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2010.01.034

The conformational analysis of anancomeric cis-ax and cis-eq 2- p-X-anilino-2-thio-4,6-dimethyl-1,3,2λ 5-dioxaphosphinanes (X=OCH 3, C 6H 11, H, Cl, CN and NO 2) is informed. In accordance with 3 J HH, 3J HP, 4 J HP, and 3 J CP coupling constants the preferred conformation in solution is a chair in both series of compounds. Structural parameters obtained through X-ray diffraction studies of the series of cis-ax and cis-eq diastereomers 1– 6, suggest that the stabilization of the axial and equatorial diastereomers in chair conformation rely on stereoelectronic n πO–σ* P–N and n πN–σ* P–O interactions, respectively. Theoretical Kohn–Sham DFT calculations support the participation of the cited stereoelectronic interactions not only to understand the conformational behavior of these systems but also to give an explanation of the observed substituent-induced chemical shift (SCS) on 31P and 15N NMR signals. Negative hyperconjugation (n–σ*) in p-X-substituted thiophosphoramidates. [Display omitted]