Conformational properties of cyclic pentaalkoxy phosphoranes: Apical–equatorial attachment and nonchair conformation of the phosphorus-containing six-membered ring

A series of phosphoranes with pentacovalent phosphorus contained in a 1,3,2-dioxaphosphorinane ring have been studied by ¹H NMR. One compound was investigated by low-temperature ¹³C NMR and another by X-ray crystallography. Although the ¹H NMR parameters observed are time-averaged, the coupling constants can be accounted for if the phosphoranes have the six-membered ring attached apical–equatorial to phosphorus and occupy in solution rapidly isomerizing boat or slightly twisted boat conformations similar to that found in the X-ray study.     

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.     

Mechanism and stereochemistry of diphosphate formation from dioxaphosphorinanes: a critical reassessment.

The mechanism of diphosphate formation from (R)-2-chloro-2-oxo-5,5-dimethyl-4-(R)-phenyl-1,3,2-dioxaphosphorinane (5a) and 2-hydroxy-2-oxo-5,5-dimethyl-4-(R)-phenyl-1,3,2-dioxaphosphorinane (6) has been investigated. The products formed are the ax-ax diphosphate 7a and the ax-eq diphosphate 7b, with no evidence in the 31P NMR spectrum for pentacoordinate chlorooxyanionic phosphoranes 9. The structure of 7bhas been established unambiguously by NMR spectroscopy, mass spectrometry, and elemental analysis, and the structures of 5a and 7a have been confirmed by X-ray crystallography. The mechanism of the crucial diphosphate-forming reaction has been probed using 18O-labeling studies. The 18O-labeling patterns are consistent with the unsymmetric ax-eq diphosphate 7b arising from selective nucleophilic attack of the axial oxygen of 6 on the chloride 5a with inversion of configuration at phosphorus. The symmetric ax-ax diphosphate 7a can be formed directly, as a result of selective nucleophilic attack of the axial oxygen of 6 on the chloride 5a with retention of configuration, but the majority arises indirectly by isomerization of the ax-eq diphosphate 7b. The isomerization apparently involves intermolecular exchange, with nucleophilic attack of the phosphate anion 6 on the equatorially substituted phosphorus atom of 7b with inversion of configuration at phosphorus.     

Nucleophilic transformations of cyclic phosphate triesters

Reactions of cyclic phosphate triesters, such as 2-ethoxy-1,3,2-dioxaphospholane 2-oxide, with Grignard reagents such as phenyl-, alkyl-, ethynyl-, and allyl-magnesium halides result in ring opening leading to the corresponding phosphonates, via nucleophilic attack of carbon on the phosphorus atom. Treatment of 2-ethoxy-1,3,2-dioxaphospholane 2-oxide with sodium borohydride yields ethyl 2-hydroxyethyl phosphite. This reaction is exclusive for the five-membered cyclic system: under these conditions acyclic phosphate triesters, such as triethyl phosphate, are unreactive and the analogous six-membered ring system, 2-ethoxy-1,3,2-dioxaphosphorinane 2-oxide reacts only partially to give unidentified phosphate esters and traces of phosphonate products. Both compounds were inert to NaBH₄.     

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.     

Solution and solid-state structures of lithiated cyclic phosphonates

Spectroscopic analysis of lithiated cyclic phospho-nates belonging to the 1,3,2-dioxaphosphorinane 2-oxide class have been examined by NMR spectroscopy in THF and by single-crystal X-ray crystallography. Lithio P-benzyl-1,3,2-dioxaphosphorinane 2-oxide (Li⁺7⁻) and lithio P-isopropyl-1,3,2-dioxaphosphorinane 2-oxide (Li⁺8⁻) are characterized by freely rotating, sp²-hybridized anions devoid of lithium–carbon contacts. The anions are most likely dimers linked through oxygen-lithium bridges. The P-isopropyl compound crystallized from TMEDA/THF as a C-lithiated dimer in which each lithium bridges a carbon and an oxygen and is solvated by one TMEDA molecule. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:209–218, 1998     

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).     

Alternating copolymerisations of dioxaphospholane and dioxaphosphorinane with γ-butyrolactone and ethylene oxide

Alternating copolymers containing phosphorus were prepared from 2-phenyl-1,3,2-dioxaphospholane, 2-phenyl-4-oxo-5,6-benzo-1,3,2-dioxaphosphorinane with ethylene oxide and γ-butyrolactone. The polymerisations took place without added catalyst. The copolymers were characterised by i.r. and NMR spectroscopy, viscosity measurements and phosphorus estimation. Key intermediates responsible for initiation and propagation of the copolymerisations were isolated and the mechanism of copolymerisation is discussed.     

Synthesis and structure of the unsymmetrical P-diastereoisomer of 1,6-dichloro-1,6-didesoxy-2,4;3,5-bis-O-(piperidinophosphoryl)-D-mannitol

Conclusions According to x-ray structural analysis, the reaction of piperidine with the chlorination product of 1,2,4;3,5,6-bis-O-(phosphintriyl)-D-mannitol gives as one product the S_PR_P-diastereoisomer of 1,6-dichloro-1,6-didesoxy-2,4;3,5-bis-O-(piperidinophosphoryl)-D-mannitol, in which the 1,3,2-dioxaphosphorinane ring with the phosphorus atom in the S-configuration is present in the boat conformation.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 426–432, February, 1989.The authors thank B. A. Arbuzov for his continuing interest in the work.     

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.     

New Synthetic Route and Characterisation of Phosphorus and Arsenic Heterocyclic Compounds

Herein we report synthetic routes for the preparation of 2-chloro-1,3,2-dioxarsenane 1 , O,O'-bis(5,5-dimethyl-1,3,2-dioxarsenane)-2,2-dimethyl-1,3-propanediol 3 , 2-chloro-1,3,2-dioxaphosphorinane 4 , and 2-fluoro-1,3,2-dioxaphosphorinane 5 . The new synthetic routes described here have the advantage to be simple, very clean and to lead to the desired compounds in very good yields. Compound 2-fluoro-1,3,2-dioxarsenane 2 also was prepared in good yield and is described here for the first time. Compounds 1-5 were fully characterized on the basis of NMR spectroscopic studies. Semi-empirical structural studies have been carried out and the results show that 1 and 2 exist as a mixture of two conformers, whereas only one conformer for 4 and 5 have been found. Variable temperature 1 H NMR studies reveal a fluxional behaviour for 1 and a mechanism for the inter-conversion between its two conformers is proposed.     

含硫环状膦酸酯衍生物的合成及其热性能

以三氯化磷、苯和硫粉为原料,用离子液体法绿色合成了硫代苯基膦酰二氯(3);3与季戊四醇或新戊二醇反应合成了两种新型含硫磷系阻燃剂--2,4,8,10-四氧杂-3,9-二磷杂螺环[5.5]十一烷-3,9-二硫-3,9-二苯(1)或5,5-二甲基-2-苯基-2-硫代-1,3-二氧-2-磷杂环己烷(2).用~1H NMR,IR,DSC和TG对其结构和性能进行了表征.结果表明,1具有良好的成炭性和热稳定性.     

Tris-phosphorylated esters of symmetrical and unsymmetrical triols

By reaction of a series of triols and monosaccharides with 5,5-dimethyl-2-chloro-1,3,2-dioxaphosphorinane their tris-phosphorylated derivatives were synthesized, and the simplest chemical transformations of the latter were studied. Structures of the obtained P(V) derivatives were confirmed by ¹H, ¹³C and ³¹P NMR spectroscopy and by the MALDI TOF mass spectrometry and X-ray structural analysis.     

Highly efficient Peterson olefination leading to unsaturated selenoamides and their characterization

The Peterson olefination of aromatic aldehydes with an alpha-silyl selenoacetamide proceeded smoothly with high stereoselectivity to give E-alpha,beta-unsaturated selenoamides in good to high yields. The reaction with aldehydes bearing alkenyl and dienyl groups gave the corresponding selenoamides bearing dienyl and trienyl groups, but the stability of the products depended on the substituents on the aromatic ring. X-ray molecular analysis disclosed that the alpha,beta,gamma,delta-unsaturated selenoamides had a nearly planar structure. In the (77)Se NMR spectra, signals were observed in the region greater than 130 ppm depending on the substituents on the aromatic ring, whereas the (1)J coupling constant between the carbon atom and the selenium atom was almost independent of the substituents. A linear relationship was observed between the chemical shifts in the (77)Se NMR spectra and Hammet sigma parameters, and this correlation was retained even when one or two alkenyl groups were introduced to alpha,beta-unsaturated selenoamides, although it became less sensitive.     

STUDIES ON ORGANOPHOSPHORUS COMPOUNDS XXX. MASS SPECTROSCOPIC INVESTIGATION OF 2-ALKYL-2-OXO-1,3,2-DIOXA-PHOSPHORINANE AND-PHOSPHEPANE

Abstract

The mass spectra of 2-alkyl-2-oxo-1,3,2-dioxa-phosphorinane and-phosphepane showed that the ring opening was in competition with the cleavage of the P[sbnd]C bond. According to the fragmentation pathway, which was dependent on the structure of exocyclic substituents on phosphorus, the 2-alkyl-2-oxo-1,3,2-di-oxa-phosphorinanes can be classified in two categories. The main process in category A was the ring opening and/or C[sbnd]C bond cleavage. While in category B the cleavage of P[sbnd]C bond was predominant. However, for 2-alkyl-2-oxo-1,3,2-dioxa-phosphepane. no matter how the structure of 2-alkyl group was, the ring opening was a dominant process.     

Oxydative Derivatisierung von 1,3,2-Dioxaphosphorinanen unter Verwendung von Tetrachlormethan als Oxydans

Oxidative Derivatization of 1,3,2-Dioxaphosphorinanes Using Carbon Tetrachloride as Oxidant 2-Alkoxy- and 2-dialkylamido-1,3,2-dioxaphosphorinanes react with CCl₄ in presence or absence of protic nucleophiles under ring opening forming acyclic derivatives of phosphates. 2-Anilido-1,3,2-dioxaphosphorinane, however, forms 2-amido-2-phenylimido-1,3,2-dioxaphosphorinanes ( 6 ) retaining the heterocyclic ring system. The latter are also obtained in the reaction of 2-dialkylamido-1,3,2-dioxaphosphorinanes with CCl₄ and aniline. 2-Amino-2-oxo-1,3,2-dioxaphosphorinanes ( 8 ) are prepared from 2-hydrido-2-oxo-1,3,2-dioxaphosphorinane ( 7 ) by means of the Atherton-Todd reaction. In combination with the Staudinger reaction the latter yields N(2-oxo-1,3,2-dioxaphosphorinanyl)phosphazenes ( 10 ).     

Spatial structure of 5-phenyl-5-oxo-2,4,6-triisopropyl-1,3,5-dioxa phosphorinane

Conclusions By means of x-ray structure analysis, it has been shown that the stereoisomer of 5-phenyl-5-oxo-2,4,6-triisopropyl-1,3,5-dioxaphosphorinane with mp 215°C has the chair conformation with all equatorial substituents of the ring atoms and axial substituents of the phosphoryl group. The conformations of the isopropyl groups are retarded relative to the ring bonds. The benzene ring at the P atom is perpendicular to the plane of the heterocycle.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.3, pp. 599–603, March, 1982.     

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.     

Equilibrium of stereoisomers of 2,4,5,6-tetraphenyl-1,3,5-dioxaphosphorinane and its derivatives

Conclusions The stereoisomers with an equatorial orientation of the phenyls on the phosphorus atom and on the carbon atoms of the ring predominate in the equilibrium of 2,4,5,6-tetraphenyl-1,3,5-dioxaphosphorinane, its oxide, and its sulfide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2136–2139, September, 1979.