Etude par Résonance Magnétique Nucléaire de dioxaphosphorinanes-1,3,2 à liaison P?N extracyclique. Exemple de changement d'orientation de la liaison P?N

The ¹H NMR spectra of several 1,3,2-dioxaphosphorinanes bearing an extracyclic P? N bond have been analysed. The ³J(POCH) couplings are strongly dependent upon the orientation of the bond around the phosphorus atom. Depending upon the nature of the bonds attached to the nitrogen atom, the dioxaphosphorinane ring may adopt either a fixed chair conformation with the P? N bond in the axial or equatorial orientation, or it may be in equilibrium between two chair conformations where the P? N bond is alternately axial or equatorial. The equilibrium is fast on the NMR time scale.     

Three-dimensional structure of phosphorus-containing heterocycles

The dipole moments and molar Kerr constants of 2-chloro-5,5-dimethyl-2-chloro-, and 4-methyl-2-chloro-1,3,2-dioxaphosphorinanes were determined. It was found that a chair conformation with an equatorial p-Cl bond is realized in all cases.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1324–1328, October, 1971.     

5,5-Bis(alkoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Synthesis and X-ray diffraction study

2,2-Bis(alkoxy-NNO-azoxy)propane-1,3-diols reacted with thionyl chloride to give previously unknown 5,5-bis(methoxy-NNO-azoxy)- and 5,5-bis(ethoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Replacement of the hydroxy groups by chlorine is a minor reaction path. According to the X-ray diffraction data, the heteroring in the molecule of 5,5-bis(methoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxide adopts a chair conformation with axial orientation of the S=O bond.     

Stereochemistry of organophosphorus cylic compounds—XV: Synthesis of tetramethylammonium salt of 2-oxo-2-thio-1,3,2,-oxazaphosphorinan and its crystal and molecular structures

2-Hydroxy-1,3,-2-oxazaphosphorinan-2-thione (5) was prepared by alkaline hydrolysis of 2-chloro-1,3,2-oxazaphosphorinan-2- thione (6). Treatment of the latter with sodium methoxide afforded the 2-methoxy-derivative 7 from which the tetramethylammonium salt of the thioacid 5 was obtained by the action of trimethylamine. The structure of this salt has been determined by the direct method and refined by least-squares to R = 0.0734, a = 12.303(4), b = 9.041(3), c = 10.419(2) Å, space group P2₁2₁2₁. The 2-oxo-2-thio-1,3,2-oxazaphosphorinanyl anion is in the chair form with the exocylic S and O atoms in an axial and equatorial position, respectively. An intermolecular H-bond between S and the endo-cyclic N atom is present in the solid-state structure.     

Conformational studies of 2-anilino-substituted 1,3,2-oxazaphospholanes

A series of 2-anilino-2-thio-1,3,2-oxazaphospholanes derived from ephedrine has been synthesized and conformationally studied by proton NMR and X-ray crystallography. The NMR data can be interpreted in terms of twist-envelope conformations in which the anilino substituents on phosphorus adopt predominantly equatorial positions. X-ray crystal structures of (2R,4S,5S)-2-anilino-2-thio-3,4-dimethyl-5-phenyl-1,3-2-oxazaphospholane, (2R,4S,5S)-2-(4-fluoroanilino)-2-thio-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholane, and (2R,4S,5S)-2-(4-methoxyanilino)-2-thio-3,4-dimethyl-5-phenyl-1,3,2-oxazaphosholane have been carried out, and these compounds adopt envelop, twist-envelope, and twist-envelope conformations, respectively, with the anilino moieties equatorial.     

ZERO VALENT METAL COMPLEXES OF 5,5-DIMETHYL-2-R-1,3,2-DIOXAPHOSPHORINANES

Abstract

The preparation and characterization of some Ni(0) and Pt(0) complexes of 5,5-dimethyl-2-phenoxy-1,3,2-dioxaphosphorinane is reported. This phosphite, which contains a single six-membered ring, displays donor-acceptor properties intermediate to P(OCH₂)₃CR and trialkyl or triaryl phosphites. The conformation of the ligand in the complexed form is proposed to be a chair ring with an axial phenoxy group.     

Stereochemistry of 1,3-Diheterocyclanes: III. Crystal and Molecular Structure and Conformations of cis- and trans-5-Phenoxy-1,3,2-dioxathiane 2-Oxides

The stereoisomers of 5-phenoxy-1,3,2-dioxathiane 2-oxide both exist as chair conformers with an axial S = O bond. The features of conformational behavior, distinguishing this diastereomeric pair from earlier studied are explained in terms of the conformational energies of substituents in the 1,3-dioxane series.     

Synthesis and equilibrium of stereoisomers of 5-phenyl-5-thio(seleno)-2-phenyl(ethoxy)-1,3, 5-dioxaphosphorinanes

Conclusions Individual stereoisomers of 2,5-diphenyl-5-thio-1,3,5-dioxaphosphorinane, 5-phenyl-5-thio-2-ethoxy-1,3,5-dioxaphosphorinane, and 5-phenyl-5-seleno-2-ethoxy-1,3,5-dioxaphosphorinane, having the chair conformation with the axial orientation of the phenyl group on the phosphorus atom and the equatorial and axial orientation of the substituent in the 2-position, have been isolated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 640–643, March, 1986.     

Phosphorinane and Enol Rings in One Molecule. Evidence for Reciprocal Stabilization of Half-Chair Conformations

Abstract.

The X-ray crystal structure of 2-(2′,4′-dioxo-3′-pentyl)-5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinane (2) reveals significant half-chair distortion of the axially oriented cisenol ring. The molecule also undergoes in-plane deformations. R(O...O) = 2.410 Å in the enol moiety indicates a very strong hydrogen bonding. The enol content, δ_OH and thermodynamic parameters for the axial-equatorial conformational and keto-enol equilibriums were obtained from ¹H, ³¹P NMR and IR measurements in comparison with the planar 4,6-dimethyl isomer (1) containing equatorially oriented enol ring. The X-ray single crystal structure of 5,5-dimethyl-2-(methoxycarbonyl-3′-oxo-2′-butyl)-2-oxo-1,3,2-dioxaphosphorinane (3) reveals the unusual half-chair conformation of the dioxaphosphorinane cycle disposed a trans-enol ring substituent. ¹H, ³¹P NMR and IR solution data support the same structure displays a strong conformational preference while the minor forms are chair conformers with an axial or equatorial cis-enol ring.     

Stereoselective formation of a P-P bond in the reaction of 2-alkoxy-2-thio-1,3,2-oxathiaphospholanes with O,O-dialkyl H-phosphonates and H-thiophosphonates

A new method for the formation of organohypophosphates containing a P-P bond under mild conditions, based on the DBU-assisted reaction of 2-alkoxy-2-thio-1,3,2-oxathiaphospholanes with O,O-dialkyl H-phosphonates or H-thiophosphonates, has been elaborated. The resulting triesters of P(1)-thio- and P(1),P(2)-dithiohypophosphoric acids, respectively, having O-methyl or O-ethyl groups, can be selectively dealkylated to form the corresponding di- or monoesters. Appropriately protected 2'-deoxyguanosine-3'-O-(2-thio-1,3,2-oxathiaphospholane) was converted into the corresponding P(1)-thio- and P(1),P(2)-dithiohypophosphate esters in a highly stereoselective manner (98%+ and 90%+, respectively).     

Conformational analysis of six-membered ring dioxaphosphinanes. Part 1: Anancomeric thiophosphates

A study of the conformation of a series of anancomeric axial and equatorial 2-aryloxy-2-thio-1,3,2λ⁵-dioxaphosphinanes 2-12 in solution and solid state is reported. In accord to the stereoelectronic theory, aryl thiophosphates substituted with electron-withdrawing (EW) groups will tend to occupy axial positions in chair ring conformations due to the stabilizing endo-anomeric (n_πO-σ_P-X^*) hyperconjugative interaction. The antiperiplanar orientation of the orbitals involved in the stereoelectronic interaction is a requirement that is fulfiled in the axial series of compounds when the ring adopts a chair conformation. Therefore, in the equatorial series of thiophosphates, the axial seeking characteristics of aryloxy-EW groups might render the molecule with distortion of the chair conformation. An opposite trend is anticipated for the less axial seeking aryl thiophosphates substituted with electron releasing (ER) groups. A detailed analysis of the ³J_HH, ³J_PH and ³J_CP coupling constants allowed us to conclude that there is no contribution of high energy twist-boat conformations in the equatorial thiophosphates substituted with aryl-EW groups in solution. In consequence, single chair conformations were found in solid state for aryl thiophosphates in both configurations. X-ray geometrical analysis of bond distances and bond angles supports clearly the participation of hyperconjugative endo-anomeric (n_πO-σ_P-OAr^*) effect in the stabilization of axial series of compounds and the participation of endo-anomeric (n_πO-σ_PS^*) effect in the stabilization of the equatorial thiophosphates in chair conformations.     

Vibrational spectra and conformational isomerism of 2-phenoxy-5,6-benz-1,3,2-dioxaphosphepins

Conclusions Using vibrational spectroscopy methods in different aggregate states and solutions with variation of the polarity of the medium, we have studied 2-phenoxy-5,6-benz-1,3,2-dioxaphosphepin and its oxo, thio, and seleno analogs. In the liquid and solutions, they exist as a conformational equilibrium of three forms: two chair forms, differing in the orientation of the phenoxyl radical, and a twist form. The population of the twist form is no more than 25%. The content of the chair conformers is determined by the solvent. In the crystal, all the compounds have the chair form with axial phenoxyl group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 844–849, April, 1989.     

Bis- and tris-bicyclophosphites of d-glucofuranoside. Unexpected catalysis of P(III/V)-oxidation by triethylamine

The synthesis and characterization of several new bicyclophosphites via reactions of (i) ethyl 1-thio-α-d-glucofuranoside 3,5,6-phosphite with acid chlorides (phthalic or butylphosphoric), (ii) ethyl 1-thio-α-d-glucofuranoside 3,5,6-phosphite with 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane and (iii) the tetraol system of ethyl 1-thio-α-d-glucofuranoside and hexaethyltriamidophosphite are reported. Unusual catalytic transformation of P(III)-compounds into the respective P(V)-spieces under extraordinary mild conditions by reaction with sulfur and selenium in the presence of triethylamine was discovered for the first time.     

Three-dimensional structures of phosphorus-containing heterocycles 50. 2-dimethylamino-2-oxo- and -2-thiono-1,3,2-oxathiaphosphorinanes

Conclusions A chair conformation with an axial orientation of the phosphoryl or thiophosphoryl group is preferable for 2-dimethylamino-2-oxo- and-2-thiono-1,3,2-oxathiaphosphorinanes. The cis isomer of 2-dimethylamino-2-oxo-4-methyl-1,3,2-oxathiaphosphorinane has a similar structure with an equatorial orientation of the 4-methyl group, while the corresponding sulfide is characterized by a trans configuration with a reoriented positioning of the substituents attached to the phosphorus atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1369–1374, June, 1989.The authors thank I. A. Litvinov and V. A. Naumov for carrying out the x-ray diffraction analysis.     

Fragmentation and isomerization reactions of phenyl substituted 2-oxo-1,3,2-dioxathianes (trimethylene sulfites)

The preparation and Grob-like fragmentation of several phenyl substituted 2-oxo-1,3,2-dioxathianes (trimethylene sulfites) have been examined. Preparation of the 4,4,6-triphenyl derivatives gives a chair S = O equatorial isomer which fragments readily in polar solvents to produce benzaldehyde and 1,1-diphenylethylene. Isomerization to an unreactive twist boat isomer occurs as a minor reaction in solution and in the solid state on prolonged storage. Activation parameters and substituent effects on the fragmentation reaction are consistent with an ionic mechanism. The diphenyl derivatives react only in the presence of boron trifluoride etherate giving mainly isomerization to the stable chair, S = O axial form; fragmentation is a minor pathway.     

Three-dimensional structure of phosphorus-containing heterocycles. 48. 2-methoxy-5,6-benz-1,3,2-dioxaphosphepine oxide and sulfide

Conclusions Using PMR spectroscopy and the dipole moment and Kerr effect methods it has been shown that 2-methoxy-5,6-benzo-1,3,2-dioxaphosphepine oxide and sulfide are characterized by solution equlibria involving two chair-like (C) conformers e-C a-C, which are shifted in favor of the e-C form; in the case of an equatorial orientation of the methoxy group equilibrium involves the gauche and anti rotamers, while in the case of an axial orientation (of the methoxy group) the gauche rotamer of the methyl group relative to P=O or P=S bond is stabilized. The presence of a twist conformer in the case of the oxide cannot be precluded from consideration.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2022–2027, September, 1988.     

Axial and Equatorial Dimethylamine Substitution on Phosphorus in the 1,3,2-Oxazaphosphorinane Ring System: Structures of 2-Dimethylamino-4-Phenyl-2H-1,3,2-Oxazaphosphorinane-2-Oxides

Single crystal x-ray structures of the diastereomeric 2-dimethylamino-4-phenyl-2H-1,3,2-oxazaphosphorinane-2-oxides, 5c and 6c, have been determined. The pair has been prepared in a straightforward manner by reaction of 3-amino-3-phenylpropanol with Mo₂P(O)Cl₂, and separated into pure forms by column chromatography. Crystal data of 5c: space group P2₁/n, a = 11.087(3), b = 6.087(6), c = 18.465(6)Å, β = 98.40(3)°, R = 0.035 for 1845 reflections. Crystal data of 6c: space group P2₁/n, a = 11.176(2), b = 6.893(2), c = 16.673(3)Å, β = 95.29(1)°, R = 0.037 for 1253 reflections. The fast-migrating 5c is cis (Ph and P = O group cis) with the configuration of 2RS, 4SR. The slow migrating 6c is trans with the configuration of 2RS, 4RS. In both structures the 1,3,2-oxazaphosphorinane rings are chair like with the P-end essentially flattened, The skeleton made up with 4-phenyl-1,3,2-oxazaphosphorinane is essentially the same. With a conformationally demanding 4-phenyl substituent, 5c has an axial Mc₂N whereas 6c has an equatorial Me₂N. For 6c, the exocyclic P-N bond has a partial double bond character the geometry about exocyclic N is planar. On the other hand, for 5c, the geometry about exocyclic N deviates considerably from planarity, the sum of the angles around N being 348.1°. In the crystalline state, the screw-related 5c molecules are hydrogen bonded whereas in the crystalline state, the centro-symmetrically related 6c molecules are paired-up by hydrogen bonds, both through the N-H and P = O system.     

Schwefel-Phosphor Heterocyclen RP(S)Sn,Darstellung, Struktur und Eigenschaften

Sulfur-Phosphorus Heterocycles RP(S)S_n, Synthesis, Structure, and Properties Sulfur-phosphorus heterocycles of the composition RP(S)S_n (R = Me, t-Bu; n = 7–5) 1a, b–3a, b have been synthesized in ring-closing reactions between the silyl or stannyl esters of trithiophosphonic acids RP(S)(SEMe₃)₂ (E = Si, Sn) and chlorosulfanes S_xCl₂ (x = 5–3). The heterocycles are fairly stable in crystalline state, in solution disproportionation to ring compounds with larger and smaller number of S-atoms, respectively, as well as oligomerization is observed. According to NMR spectroscopic investigations the S? P heterocycles exhibit the following structures 1. MeP(S)S₇ ( 1a ), eight-membered ring showing two crown conformations that differ in the orientation (axial, equatorial) of the Me-group; t-BuP(S)S₇ ( 1b ), eight-membered ring with crown conformation (t-Bu = equatorial). 2. RP(S)S₆ ( 2a, b ), seven-membered rings with twist-chair conformation. 3. RP(S)S₅, six-membered rings, R = Me ( 3a ) chair conformation (Me = axial), R = t-Bu ( 3b ) chair conformation (t-Bu = equatorial) and twist-boat conformation. In crystalline state 1a only exists in the crown conformation with axial orientation of the Me-group. In solution a fast conformational interconversion between the two isomers of 1a and of 3b has been detected by dynamic NMR measurements. Furthermore t-BuP(S)S₅ ( 3b ) is in a temperature and concentration dependent equilibrium with its dimer and probably also with oligomeric forms.     

Crystal and molecular structure of 5,5-BIS(hydroxymethyl)-2-OXO-2-[l-(2-trifluoromethyl-3,3,3-trifluoropropioneamido)-1-trifluoromethyl-2,2,2-trifluoroethyl]-1,3,2-dioxaphosphorinane

The crystal and molecular structure of 5,5-bis(hydroxymethyl)-2-oxo-2-[1-(2-trifluoromethyl-3,3,3-tri-fluoropropioneamido)-1-trifluoromethyl-2,2,2-trifluoroethyl]-1,3,2-dioxaphosphorinane (I) - an effective inhibitor of phosphorolytic enzymes - has been determined by X-ray diffractometry. Crystals I are monoclinic: space group P2₁/c, a = 9.962(3), b = 20.468(3), c = 9.527(3) å, Β = 108.04(2)?, Z = 4; R = 0.061 for 3065 independent reflections with I ≥ 3Σ. In a sterically strained molecule I, the coordination polyhedron of the P atom is a distorted tetrahedron with an elongated exocyclic P-C bond [1.906(2) å]. The six-membered heterocycle of I has a distorted chair conformation with a significantly flattened angle at the P atom. In the crystal structure, molecules I are linked into centrosymmetric H-dimers by a pair of strong H-bonds of O-H...O=P type and also into infinite (along the z axis) chains by H-bonds of N-H...O = C and C-H...O = C type.     

Conformational analysis of 4-methyl-2-trimethylsiloxy-1,3,2-dioxaphosphinane

Conformational analysis of 4-methyl-2-trimethylsiloxy-1,3,2-dioxaphosphinane was performed by the dipole moment method and quantum-chemical calculations. The 1,3,2-dioxaphosphinane heteroring was found to adopt a chair conformation with equatorial orientation of the 4-methyl group and axial orientation of the irregular trimethylsiloxy substituent. The conformational equilibrium involves non-eclipsed gauche and trans conformers (the latter prevailing) interconvertible through rotation about the exocyclic P-O bond.