Conformational studies of 5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinanes by means of dipole moments,lonization potentials and CNDO/2 calculations

CNDO/2 calculations are used for investigating the conformation of a series of 5,5-dimethyl-2-oxo-1, 3,2-phosphorinanes. The results agree with IR and NMR investigations. To obtain further experimental information dipole moments and ionization potentials are measured. The experimental measurements, together with calculated quantities, give valuable information about the conformation of these compounds in solution.     

NMR and stereochemical studies of non aromatic heterocyclic compounds—II : 13C and 31P NMR of 2-methoxy-1,3,2-dioxaphosphorinanes

¹³C and ³¹P chemical shift data for eight 2-methoxy-1,3,2-dioxaphosphorinanes are reported. Examination of pairs of geometrical isomers, which differ only in the orientation of the OMe substituent on P^III, have shown that both the ³¹P and the ¹³C signals of C_4,6 atoms appear 3–4 ppm at higher field when the OMe is axial compared with the equatorial isomer. This observation can be associated with the 1–3 syn diaxial interaction between the phosphorus axial substituent and the axial hydrogens on C_4,6 and should thus constitute, in the future, a supplementary tool for the structural analysis of this kind of compound. Important long range δ effects were observed both on ¹³C and especially on ³¹P chemical shifts. It is suggested that the high field δ_e effects could reflect a direct stereoelectronic interaction between the P atom and the cyclic C-5 atom. This interpretation is supported by a study of the ³¹P…¹³C coupling constants and their stereochemical dependence.     

反式-2-取代硫代氨基脲基-4-芳基-5,5-二甲基-2-氧-1,3,2-二氧磷杂环己烷的立体选择性合成及立体化学研究

首先合成了重要的磷酰异硫氰酸酯中间体3, 然后便捷、高产率且立体选择性地合成了反式-2-取代硫代氨基脲基取代的新型六元磷杂环, 其立体化学通过2D NOESY NMR确证. 所有合成的化合物均进行了元素分析和光谱表征, 其中目标产物的13C NMR表征为1,3,2-二氧磷杂环己烷衍生物的碳骨架表征提供了难得的依据. 在溶剂DMSO-d6中, 所有产物均异构化, 生成磷原子的差向异构体. 这一研究结果证明了C4—H 以及31P NMR谱图与立体结构的相关性.     

Conformational and configurational analysis of 2-phenoxy-2-oxo-1,3,2-dioxaphosphorinanes. Conformational and configurational dependence upon conformation of the diol precursor

Diastereomeric 5-tert-butyl-4-methyl-2-phenoxy-2-oxo-1,3,2-dioxaphosphorinanes were synthesized, and studied by NMR and computational methods in order to determine their predominant conformations as well as their relative configurations. The study was performed assuming a novel criteria, in which, the conformation and configuration of the diastereomeric 5-tert-butyl-4-methyl-2-phenoxy-2-oxo-1,3,2-dioxaphosphorinanes depend upon the conformation of the corresponding diol precursors. In other words, the orientation or pseudo orientation of the groups into the ring framework of the heterocyclic is initially acquired by the direct phosphorylation reaction with the diol precursor in the most stable conformation, and then, once the heterocyclic is formed, the final conformation is dictated by stereoelectronic and steric effects.     

Conformational analysis of 2-methyl-5-alkyl- and 5-aryl-1,3,2-dioxaborinanes

Quantum chemical study of conformational isomerization of 2-methyl-5-alkyl- and 5-aryl-1,3,2-dioxaborinanes using RHF/6-31G(d) method led to the conclusion that the equilibrium between equatorial and axial sofa conformers is shifted to the latter form. Based on the experimental and theoretically calculated vicinal coupling constants J _HH the quantitative conformational composition and the values of ΔG ⁰ for substituents at the C⁵ ring atom were established.     

1H, 13C and 31P NMR Studies of the Stereochemistry of Chiral 2-Substituted (4R,6R)-Dimethyl-1,3,2-dioxaphosphorinanes

Abstract

¹³C, ¹H and ³¹P NMR investigations have been carried out tc determine the ring stereochemistry and phosphorus configuration for four chiral (4R,6R)-2R-4, 6-dimethyl-1,3,2-dioxaphosphorinane derivatives, 1-4 (2R=Cl, Ph, OMe and Ot-Bu, respectively).     

13C nuclear magnetic resonance and conformational analysis of 5-chloro-2-oxo-1,3,2-dioxathianes

The ¹³C NMR chemical shifts in CDCI₃ for eight cyclic sulphites, chlorinated at C-5, are reported. The α-and β-deshielding effects and the γ-shielding effects for the chlorine substituent are compared with similar effects in the 1,3-dioxane series and with the effects arising from methyl groups in the sulphite series. The study of two conformational equilibria shows that it is difficult to use ¹³C NMR spectroscopy for the conformational analysis of cyclic sulphites because of the frequent participation of twist forms, with 1,4- and 2,5-axes, to these equilibria.     

1, 2λ5-azaphosphinines and a new 1λ5, 3λ5-. Diphosphinine

The 1,2-azaphosphinine, 9 , and the 1,3-diphosphinine, 10 , can be isolated from a mixture resulting from the reaction of 1,1,3,3-tetrakis(dimethylamino)-1λ⁵,3λ⁵-diphosphete, 1 , and ethyl isothiocyanate. The reaction of 1 with phenyl isothiocyanate yields the 1,2-azaphosphinine, 16 . Mechanisms for the formation of the compounds 9 , 10 , and 16 are suggested. The properties, the NMR, mass, and IR spectra, and the molecular and crystal structures of 9 and 10 are described and discussed.     

Conformational analysis—VIII : 1H NMR conformational study of 5-methyl-, 2,5-dimethyl- and 2,2,5-trimethyl-4-oxo-1,3-dioxans

Substituent effects on ¹H chemical shifts of a large number of methyl-substituted 4-oxo-1,3-dioxans have been estimated and shown to be additive for compounds with a uniform half-chair conformation. The additivity rule fails, however, if the substitution pattern forces the ring into a non half-chair conformation. The ring conformations of 5-methyl-, cis- and trans-2,5-dimethyl- and 2,2,5- trimethyl-4-oxo-1,3-dioxans have been clarified by NMR and through acid-catalyzed equilibration of the epimeric 2,5-dimethyl derivatives.     

P,P′-(2,5-Dimethoxy-3,6-dimethyl-2,5-dioxo-2λ5,5λ5-[1,4,2,5]dioxadiphosphinan-2,5-diyl)-bis-phosphonsäuretetramethylester

P,P′-(2,5-Dimethoxy-3,6-dimethyl-2,5-dioxo-2λ⁵,5λ⁵-[1,4,2,5]dioxadiphosphinane-2,5-diyl)-bis-phosphonic acid tetramethylester The title compound 1 is formed by reaction of the corresponding phosphonic acid 2 and orthoformicacidmethylester as a mixture of four stereoisomeres. The RRSS isomer was separated. It crystallizes in the triclinic space group P ?1 with a = 649.2 pm, b = 976.1 pm, c = 1 571.7 pm, α = 80.9°, β = 88.1°, γ = 78.6° and Z = 2. The ³¹P and ¹³C NMR spectra (4 and 5 spin systems) are discussed.     

P,P′-(2,5-Dihydroxy-3,6-dimethyl-2,5-dioxo-2λ5,5λ5-[1,4,2,5]-dioxadiphosphinan-2,5-diyl)-bis-phosphonsäure

P,P′-(2,5-Dihydroxy-3,6-dimethyl-2,5-dioxo-2λ⁵,5λ⁵-[1,4,2,5]dioxadiphosphinane-2,5-diyl)-bis-phosphonic Acid The tetrahydrate 1 of the title compound crystallizes in the monoclinic space group P2₁/c with a = 845.8, b = 1 098, c = 981.7 pm, β = 113.02° and Z = 2. The anions of the oxonium compound (H₃O⁺ · H₂O)₂(C₄H₁₀O₁₂P₄^2?) are layered by hydrogen bridges. The ¹H, ¹³C and ³¹P NMR spectra (4 and 5 spin systems) are discussed.