Stereospecific conversion of cyclic phosphorothioates into chlorophosphates

The reaction of the individual diastereoisomeric cyclic phosphorothioates 2a, 2b in the trans-2,4,7-trioxa-3-phosphabicyclo (4.4.0) decane and 4a, 4b in the trans-2,4,7-trioxa-3-phosphabicyclo (4.3.0) nonane series with sulphuryl chloride affords the corresponding sulphenyl chlorides 5a, 5b, 6a, 6b with retention of the configuration of the phosphorus atom. The reaction of the latter with phosphorus trichloride leads stereospecifically to the chlorophosphates 7a, 7b, 8a and 8b with full retention of configuration at phosphorus.     

Optically active P-chiral phosphinoselenoic amides: stereochemical outcome at the P-stereogenic center in the synthesis of these substances and their characterization

A variety of optically active P-chiral phosphinoselenoic amides were synthesized with high efficiency by reacting racemic P-chiral phosphinoselenoic chlorides with optically active lithium amides. Some of the diastereomers of the amides were separated by column chromatography on silica gel. The absolute configurations of the phosphinoselenoic amides were determined by X-ray molecular structure analyses. Optically active P-chiral phosphinoselenoic chlorides were also reacted with optically active lithium amide. The reaction proceeded predominantly with inversion of configuration, but also involved retention of stereochemistry at the phosphorus atom during the substitution reaction.     

Stereochemistry of the acyclic phosphono- and phosphino-thiocyanide isomerisation into corresponding isothiocyanidates : Synthesis of optically active thiocyanidates > P(O)SCN isothiocyanidates > P(O)NCS,isocyanidates > P(O)NCO and related phosphorylated derivatives of carbonic acid

Optically active t-butylphenylphosphinothiocyanidate Bu^tPhP(O)SCN 3 and t-butyl-O-methyl-phosphonothiocyanidate Bu^t(MeO)P(O)SCN 7 have been prepared by condensation of the corresponding sulphenyl chlorides > P(O)SCl with trimethylsilylcyanide and isomerised into optically active t-butyl-O-methyl-phos-phonoisothiocyanidates Bu^t(MeO)P(O)NCS 8. Chirality at P in and the optical purity of the chiral phosphino (phosphono) thiocyanidates and isothiocyanidates have been determined by chemical correlations. It has been demonstrated that the thiocyanate ion and amine catalysed thiocyanidate-isothiocyanidate isomerisation > P(O)SCN → > P(O)NCS occurs stereospecifically with inversion of configuration at the P center. This result can be rationalized by postulation of a phosphorane intermediate, formed by nucleophilic attack of the SCN^- anion on phosphorus, in which thiocyanate and isothiocyanate groups occupy apical positions. In connection with these studies a number of novel optically active phosphorylated derivatives of carbonic acid, > P(O)NHCSNHR, > P(O)NCCl₂, > P(O)NCO and > P(O)NHCOOBu^t, have also been synthesised.     

Reaction of phosphorus trichloride with carboxylic acids

The reaction of phosphorus trichloride with a number of monobasic carboxylic acids has been studied and the optimum ratio of reactants for the yield of acid chlorides has been established. Based on analysis and the data from³¹P NMR spectroscopy of the phosphorus-containing products from this reaction it is shown that at 402-50°C a mixture of P-H acids having a predominant content of pyrophosphorous acid is formed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 428–432, February, 1990.     

Derivatizing agents from phosphorus trichloride and terpenyl tartrates for determining the enantiomeric purity of alcohols

Heterocyclic phosphorous acid chlorides, prepared from C₂-symmetric menthyl, borneyl, or fenchyl tartrates and phosphorus trichloride, are inexpensive derivatizing agents for determining the enantiomeric purity of alcohols via phosphorus NMR. The most versatile agent identified from this study, a (1R,2S,5R)-menthyl (R,R)-tartrate-derived 2-chloro-1,3,2-dioxaphospholane, gives, upon esterification with chiral alcohols, diastereomeric phosphites showing phosphorus NMR-shift dispersions between 0.1 ppm and 1.5 ppm.     

Nucleophilic Substitution at Tetracoordinate Phosphorus. Stereochemical Course and Mechanisms of Nucleophilic Displacement Reactions at Phosphorus in Diastereomeric cis- and trans-2-Halogeno-4-methyl-1,3,2-dioxaphosphorinan-2-thiones: Experimental and DFT Studies

Geometrical cis- and trans- isomers of 2-chloro-, 2-bromo- and 2-fluoro-4-methyl-1,3,2-dioxaphosphorinan-2-thiones were obtained in a diastereoselective way by (a) sulfurization of corresponding cyclic P^III-halogenides, (b) reaction of cyclic phosphorothioic acids with phosphorus pentachloride and (c) halogen–halogen exchange at P^IV-halogenide. Their conformation and configuration at the C₄-ring carbon and phosphorus stereocentres were studied by NMR (¹H, ³¹P) methods, X-ray analysis and density functional (DFT) calculations. The stereochemistry of displacement reactions (alkaline hydrolysis, methanolysis, aminolysis) at phosphorus and its mechanism were shown to depend on the nature of halogen. Cyclic cis- and trans-isomers of chlorides and bromides react with nucleophiles (HO⁻, CH₃O⁻, Me₂NH) with inversion of configuration at phosphorus. DFT calculations provided evidence that alkaline hydrolysis of cyclic thiophosphoryl chlorides proceeds according to the S_N2-P mechanism with a single transition state according to the potential energy surface (PES) observed. The alkaline hydrolysis reaction of cis- and trans-fluorides afforded the same mixture of the corresponding cyclic thiophosphoric acids with the thermodynamically more stable major product. Similar DFT calculations revealed that substitution at phosphorus in fluorides proceeds stepwise according to the A–E mechanism with formation of a pentacoordinate intermediate since a PES with two transition states was observed.     

Halogenative kinetic resolution of β-aryloxy cyclic alcohols: chiral BINAP-mediated SN2 displacement of hydroxy groups by chlorides with inversion of stereochemistry

A series of optically active cyclic trans-β-aryloxy alcohols have been obtained by non-enzymatic kinetic resolution of the corresponding racemic aryloxy cyclic alcohols using commercially available (S)-BINAP and NCS by S_N2 halogenation of a hydroxy group. The product, cis-β-aryloxy chlorides, was also obtained in optically active form with inversion of the stereochemistry.     

DMSO-catalyzed chlorination of alcohols using N-phenylbenzimidoyl chloride

N-phenylbenzimidoyl chloride has been demonstrated as an efficient chlorination reagent catalyzed by dimethyl sulfoxide (DMSO) in conversion of alcohols to corresponding chlorides. The reaction conditions were mild, and most of the substrates gave satisfactory yields. The configuration inversion of the chlorination was proved using optically active phenyl alcohols. The amount of DMSO can be as low as 0.001 eq without reducing the efficiency of the chlorination. A plausible mechanism for the reaction was proposed and proved by experiments. The reaction is stereoselective and potentially chemoselective among primary benzyl alcohols, secondary benzyl alcohols, and unactivated aliphatic alcohols.     

Reactions of phosphorus halides with urethane

By the reaction of phosphorus trichloride, thiophosphoryl chloride, phosphorus oxychloride and phosphorus pentachloride with urethane in stoichiometric ratio 1:1 or 1:2 in benzene, compounds of the type

and

(X = S, O or Cl; n = 1 or 2) have been synthesized. A probable mechanism for their formation has also been suggested.     

γ-Sulphenylation of αβ-unsaturated aldehydes,ketones, and esters: the use of O-silylated dienolates

Phenyl sulphenyl chloride is a γ-selective electrophile in its reaction with O-silylated dienolates.     

Organophosphorus Synthesis Without Phosphorus Trichloride: The Case for the Hypophosphorous Pathway

Abstract

The vast majority of organophosphorus compounds is currently synthesized from phosphorus trichloride (PCl₃), even though the final consumer products do not contain reactive phosphorus–chlorine bonds. In order to bypass phosphorus trichloride, significant interest has been devoted to functionalizing elemental phosphorus (P₄, the precursor to PCl₃), red phosphorus (P_red), or phosphine (PH₃). Yet, other industrial-scale precursors are hypophosphorous derivatives (H₃PO₂ and its alkali salts), but their use as phosphorus trichloride replacements has been completely overlooked. Here, the case is made for an alternative approach to the industrial synthesis of organophosphorus compounds based on hypophosphites.     

PPh3-Mediated Nucleophilic Sulfonation of Sulfonyl Chlorides with Arynes: Access to Manifold Aryl Sulfones

Sulfonyl chlorides are a class of cheap and readily available basic chemicals, which have routinely served as electrophilic reagents in their chemical transformations. Herein, we disclose a novel PPh₃-mediated nucleophilic sulfonation method of sulfonyl chlorides with arynes. Different from the classical P(III)-mediated reductive deoxygenation reaction of sulfonyl chlorides, the valence state of the sulfur atom has not been changed. This protocol exhibits broad functional group tolerance and provides a direct approach to a variety of aryl and alkyl sulfones.     

Concurrent synthesis of vanillin and isovanillin

A method for concurrent synthesis of vanillin and isovanillin has been developed by a nonregioselective Vilsmeier–Haack reaction of O-alkyl guaiacols. O-Alkylation of guaiacol provided the corresponding O-alkyl guaiacol (1), which was then formylated with N-methylformanilide/phosphorus oxychloride to give a mixture of 4-alkoxy-3-methoxy-benzaldehyde (2) and 3-alkoxy-4-methoxybenzaldehyde (3). Finally, the obtained mixture underwent a selective dealkylation by anhydrous aluminium trichloride, while leaving methyl groups intact to simultaneously achieve the significant fine chemicals vanillin and isovanillin.     

The chemistry of the Western Australian rutaceae—VI : Two novel coumarins from Eriostemon brucei

Eriobrucinol (1) has been related to hydroxyeriobrucinol (4) by oxidation of the methyl ether of the latter to a ketone (8) and desulphurisation of the derived thioketal. The structures of the coumarins are derived from chemical and spectroscopic arguments. Assignment of the all cis configuration for the alicyclic system is supported by evidence for conformational inversion in the 1′ hydroxy derivative (11).     

The NMR spectra of some 3-coordinate phosphorus compounds containing chloromethyl and isopropyl groups

Analysis of the proton NMR spectra of Pr¹PCINMe₂ indicates magnetic non-equivalence of the methyl groups due to the adjacent asymmetric phosphorus atom. High temperatures, or the addition of chloride ion, induce an exchange reaction with inversion of configuration at phosphorus. The corresponding fluoride is configurationally stable at high temperatures. The compounds CICH₂PXNR₂ (X = Cl, F; R = Me, Et) have non-equivalent protons in the chloromethyl group. The two HCP coupling constants in the chlorides of this series are of opposite sign, whereas in the fluorides they are of the same sign.     

Reactions of atomic carbon with acyl chlorides

Reactions of arc-generated carbon atoms with acyl chlorides proceed by two distinct mechanistic pathways depending on the nature of the alkyl group in the substrate. Acetyl chloride affords vinyl chloride from the putative chloromethylcarbene produced by deoxygenation, whereas pivaloyl chloride gives t-butyl chloride as the predominant product via a chain reaction from the initially generated pivaloyl radical. When the alkyl group is isopropyl, both pathways are implicated.     

Optically active trivalent phosphorus compounds—I: Diastereoisomeric o-menthyl ethylphenylphosphinites: synthesis,chirality at phosphorus and stereochemistry of nucleophilic displacement reaction

The reaction between racemic ethylphenylchlorophosphine and menthol has been found to give a mixture of diastereoisomeric O-menthyl ethylphenylphosphinites (4) in unequal ratio. The diastereoisomeric content depends mainly on the tertiary amine used for the condensation. The chirality at phosphorus in the diastereoisomeric esters (4a and 4b) has been assigned by means of chemical correlation (conversion into optically active methylethylphenylphosphine oxide) and proton NMR spectra. It has been demonstrated that nucleophilic substitution at phosphorus in 4 occurs with inversion of configuration.     

Oxaphosphetane versus betaine formation in epoxide ring opening by PPh3: a mechanistic probe by ab initio and DFT modeling

Ab initio and density functional investigations on the deoxygenation of cis-2,3-dimethylepoxide by PPh₃ reveal a two-step mechanism. Simultaneous ring-opening and C-C bond rotation facilitates oxaphosphetane formation thereby ruling out the formation of a betaine intermediate and is consistent with the inversion of stereochemistry observed in the reaction.     

A novel reaction of β,β′-dihydroxy acids or esters with vanadium(V) trichloride oxide. New entry to the stereoselective synthesis of α-fluoro-α,β-unsaturated acids and esters

β,β′-Dihydroxy carboxylic acids and esters, readily prepared from dibromofluoroacetate and aldehydes, underwent deoxygenation, followed by elimination of aldehyde by the action of vanadium(V) trichloride oxide at the reflux temperature of chlorobenzene for 1 h to afford the Z isomers of α-fluoro-α,β-unsaturated acids and esters, respectively, in fair to good yields. This reaction provides a new alternative entry to the stereoselective synthesis of such fluoro compounds.     

New methods for the Preparation of Nitrosyl Chloride

A pure sample of nitrosyl chloride has been prepared either by reaction of phosphorus trichloride with concentrated nitric acid or by reaction of phosphorus trichloride with sodium nitrate in presence of water. The nitrosyl chloride gas has been characterized by i.r. spectral data and elemental analysis.