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

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• 作者：Zaira Domí ; nguez ; Marcelo Galvá ; n ; Ma. Teresa Cortez ; Magali Salas ; Rocí ; o Meza ; Marco A. Leyva-Ramirez ; Barbara Gordillo
• 关键词：Dioxaphosphinanes ; Thiophosphoramidates ; Conformation ; NMR ; SCS and LFER correlations ; X-ray crystal structures ; Negative hyperconjugation
• 刊名：Tetrahedron
• 出版年：2010
• 出版时间：13 March 2010
• 年：2010
• 卷：66
• 期：11
• 页码：2066-2076
• 全文大小：639 K

文摘

The conformational analysis of anancomeric cis-ax and cis-eq 2-p-X-anilino-2-thio-4,6-dimethyl-1,3,2λ⁵-dioxaphosphinanes (X=OCH₃, C₆H₁₁, H, Cl, CN and NO₂) is informed. In accordance with ³J_HH, ³J_HP, ⁴J_HP, and ³J_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.