DER OXIDATIVE ABBAU VON THIOPHOSPHIN- THIOPHOSPHON- UND THIOPHOSPHORSÄUREESTERN MIT HYPOCHLORIT

Abstract

The thioesters R¹R²P(X)SR (X=O,S) 1 to 4 are degradated oxidatively forming R¹R²P(O)OH and R-SO³H. The influence of the following parameters on the oxidation course is investigated using standard conditions: pH, concentration of the hypochlorite, quality of the organic phase and cooperation of phase transfer catalysts and hypochlorite cations.

The thioesters 1 to 4 are degradated by hypochlorite with different rates depending on the type of the ligands R¹ and R² and the employment of an optimal pH. An analytical evaluation is possible.

Die Thioester R¹R²P(X)SR (X=O,S) 1 bis 4 werden durch Hypochlorit oxidativ zu R¹R²P(O)OH und RSO₃H abgebaut. Der Einfluß folgender Parameter auf den Oxidationsverlauf unter Standardbedingungen wird untersucht: pH, Hypochloritkonzentration, Art der organischen Phase, Mitwirkung von Phasentransfer-Katalysatoren und der Hypochlorit Kationen.

Die Thioester 1 bis 4 werden mit Hypochlorit in Abhängigkeit vom Typ der Liganden R¹ und R² und nach Einstellen eines optimalen pH-Wertes unterschiedlich schnell abgebaut. Dieser Unterschied ist analytisch auswertbar.     

Rate constants for the reaction of the chloromethyne radical with alkynes

Absolute rate constants were measured for the gas phase reactions of the CCl(X?²Π) radical produced in the flash photolysis of CHBr₂Cl with a representative series of alkynes. The rate of addition to the triple bond follows the trend established for the addition CCl(X?²Π) to olefinic double bonds and the acetylenic triple bond by the latter reagent. A linear correlation between log k and ionization potentials of the alkynes reflects the electrophilic nature of the reaction.     

Reaction of Frustrated Lewis Pairs with Ketones and Esters

The frustrated Lewis pair (FLP) Mes₂PCH₂CH₂B(C₆F₅)₂ ( 1 ) reacts with an enolizable conjugated ynone by 1,4‐addition involving enolate tautomerization to give an eight‐membered zwitterionic heterocycle. The conjugated endione PhCO‐CH?CH‐COPh reacts with the intermolecular FLP tBu₃P/B(C₆F₅)₃ by a simple 1,4‐addition to an enone subunit. The same substrate undergoes a more complex reaction with the FLP 1 that involves internal acetal formation to give a heterobicyclic zwitterionic product. FLP 1 reacts with dimethyl maleate by selective overall addition to the C?C double bond to give a six‐membered heterocycle. It adds analogously to the triple bond of an acetylenic ester to give a similarly structured six‐membered heterocycle. The intermolecular FLP P(o‐tolyl)₃/B(C₆F₅)₃ reacts analogously with acetylenic ester by trans‐addition to the carbon–carbon triple bond. An excess of the intermolecular FLP tBu₃P/B(C₆F₅)₃, which contains a more nucleophilic phosphane, reacts differently with acetylenic ester examples, namely by O? C(alkyl) bond cleavage to give the {R‐CO₂[B(C₆F₅)₃]₂^?}[alkyl‐PtBu₃⁺] salts. Simple aryl or alkyl esters react analogously by using the borane‐stabilized carboxylates as good leaving groups. All essential products were characterized by X‐ray diffraction.     

Gold(I) Complexation with Trialkyl/Triaryl Phosphine Selenide Ligands

Abstract

A number of phosphine selenide ligands and their gold(I) complexes of general formula R₃P?Se?Au?X (where X is Cl^?, Br^? and CN^? and R = phenyl, cyclohexyl and tolyl) were prepared. The complexes were characterized by elemental analysis, IR and ³¹P NMR spectroscopic methods. In the IR spectra of all complexes a decrease in frequency of P?Se bond upon coordination was observed, indicating a decrease in P?Se bond order. ³¹P NMR showed that the electronegativity of the substituents is the most important factor determining the ³¹P NMR chemical shift. It was observed that phosphorus resonance is more downfield in alkyl substituted phosphine selenides, as compared to the aryl substituted ones. Ligand disproportionation in the complex Cy₃P?SeAuCN in solution to form [Au(CN)₂]^? and [(Cy₃P?Se)₂Au]⁺ was investigated by ¹³C and ¹⁵N NMR spectroscopy.     

THE PHOSPHAZENES–STRUCTURAL PARAMETERS AND THEIR RELATIONSHIPS TO PHYSICAL AND CHEMICAL PROPERTIES

Abstract

A systematic study of crystallographic data has revealed a number of correlations between structural parameters, (e.g., bond angles, bond lengths, dihedral angles) and physical and chemical properties in phosphazenes and related compounds. These include (a) endocyclic bond angles NPN and PNP and their relationships to group electronegativities; (b) endocyclic bond angles NPN and PNP in geminal cyclotriphosphazatrienes, N₃P₃RR′X₄ (X = F, Cl) and their relationships to basicity; (c) deviations from some relationships due to ring puckering and the use of mathematical techniques to “flatten out” these rings; (d) ³⁵Cl nuclear quadrupole resonance frequencies and P–Cl bond lengths and other relationships; (e) exocyclic bond angles viz. OPO, NPN, ClPCl, CPC etc. versus ³¹P NMR chemical shifts; (f) ring compression and deformation and unusual mass spectrometric and bulk polymerisation properties; (g) relationships in phosphazenylcyclophosphazenes between crystal structure, ⁴ J(PP) coupling constants, basicity and conformation; (h) relationships between spin-spin coupling constants, dihedral angles in, and conformations of, spiroderivatives of cyclophosphazenes–trigonal planar versus pyramidal nitrogen atoms.     

Construction of Extended and Polymeric 1,3-Dithiolane and Tetrathiafulvalene Derivatives using Cycloaddition of Bun 3P.CS2

Abstract

Cycloaddition of the adduct between Buⁿ ₃P and CS₂ to strained double bonds such as in norbornene gives novel zwitterionic products such as 5. This dissociates to the ylide 4 so that carrying out the reaction in the presence of an aldehyde leads to a Wittig reaction to give 2-alkylidene-1,3-dithiolanes. The compound 5 reacts with acetylenic dipolarophiles by cycloaddition accompanied by loss of Buⁿ ₃P to give dihydro-TTF derivatives. Both these reaction types also occur for norbornadiene and by using this together with dialdehydes or diacetylenes a range of new sulfur-rich extended and polymeric structures have been obtained.     

14N and 35Cl NQR studies of organophosphorus compounds

¹⁴N and ³⁵Cl NQR spectra have been investigated for 24 organophosphorus compounds using a pulse technique. The electron populations of the nitrogen lone pair orbital and the N? P bond are calculated according to the Townes and Dailey method. The experimental data are interpreted assuming a partial double bond character of the N? P bond due to the p_π? d_π interaction and p_π? σ conjugation of the lone pair electrons of the nitrogen atoms. The effect of the different nature of substituents X on the N? P bond populations is observed in X ? PR_n (R₂N)_3-n molecules (where X is O, S, Se, or lone pair electrons and n = 0, 1, 2). It can be seen from this dependence that the effective electronegativity of the phosphorus atom is largest in selenophosphoramidates and falls in the sequence P?Se > P?S > P?O > P.     

Construction of Extended and Polymeric 1,3-Dithiolane and Tetrathiafulvalene Derivatives using Cycloaddition of Bun 3PßCS2

Abstract

Cycloaddition of the adduct between Buⁿ ₃P and CS₂ to strained double bonds such as in norbornene gives novel zwitterionic products such as 5. The compound 5 reacts with acetylenic dipolarophiles by cycloaddition accompanied by loss of Buⁿ ₃P to give dihydro-TTF derivatives. The corresponding reaction also occurs for norbornadiene and by using this a range of new extended sulfur-rich structures and substituted TTFs have been obtained.     

STUDIES OF HETEROCYCLIC COMPOUNDS: VI1 THE MASS SPECTRA OF SOME 2-THIOPHENEMERCURIC DERIVATIVES

Abstract

The mass spectra of some 2-thiophenemercuric derivatives are determined and the fragmentation interpretations are based on mechanistic analogy and supported in some cases by metastable peaks and low energy mass spectra. They all fragment ultimately to the 2-thienyl cation formed either through a two-step process, by cleavage of Hg[sbnd]X bond to give the 2-thienylmercuric cation, followed by extrusion of mercury, or by a one-step process through cleavage of carbon-mercury bond. Their base peaks being the C₃H₃ ⁺ion (m/e 39).     

Complexes H2CO:PXH2 and HCO2H : PXH2 for X=NC,F, Cl,CN, OH,CCH, CH3, and H: Pnicogen Bonds and Hydrogen Bonds

Ab initio MP2/aug’-cc-pVTZ calculations have been carried out to investigate H₂CO : PXH₂ pnicogen-bonded complexes and HCO₂H : PXH₂ complexes that are stabilized by pnicogen bonds and hydrogen bonds, with X=NC, F, Cl, CN, OH, CCH, CH₃, and H. The binding energies of these complexes exhibit a second-order dependence on the O−P distance. DFT-SAPT binding energies correlate linearly with MP2 binding energies. The HCO₂H : PXH₂ complexes are stabilized by both a pnicogen bond and a hydrogen bond, resulting in greater binding energies for the HCO₂H : PXH₂ complexes compared to H₂CO : PXH₂. Neither the O−P distance across the pnicogen bond nor the O−P distance across the hydrogen bond correlates with the binding energies of these complexes. The nonlinearity of the hydrogen bonds suggests that they are relatively weak bonds, except for complexes in which the substituent X is either CH₃ or H. The pnicogen bond is the more important stabilizing interaction in the HCO₂H : PXH₂ complexes except when the substituent X is a more electropositive group. EOM-CCSD spin-spin coupling constants ^1pJ(O−P) across pnicogen bonds in H₂CO:PXH₂ and HCO₂H : PXH₂ complexes increase as the O−P distance decreases, and exhibit a second order dependence on that distance. There is no correlation between ^2hJ(O−P) and the O−P distance across the hydrogen bond in the HCO₂H : PXH₂ complexes. ^2hJ(O−P) coupling constants for complexes with X=CH₃ and H have much greater absolute values than anticipated from their O−P distances.     

NMR Studies of Restricted Rotation in Aminatophosphorus(1+) Salts

Abstract

A series of aminatophosphorus(1+) salts were synthesized as potential fungicides. Proton NMR of a set of compounds 1 within this series were observed to show selective line broadening of the methylene protons indicating a dynamic process which is slow on the NMR time scale. X-ray crystal structures of two of the compounds in the series showed a relatively planar nitrogen eliminating nitrogen inversion as the source of the observed line broadening. The methylene protons appeared as a sharp doublet (³J_PH = 3.6 Hz) at room temperature when R=OCH₃, a broad singlet when R=OCF₃, and a sharp multiplet consistent with the AB portion of an ABX (X = ³¹P) spin system when R=SCH. Examination of the temperature dependence of the spectra revealed that the observed lineshape and temperature effects were consistent with slow rotation about the N-Ph bond and dependent primarily upon the size of the substituent R. Thus the slow rotation was thought to be due to steric factors and not the influence of electronic effects of the substituent R on the P-N bond. Rotation rates estimated from NMR lineshape analysis and plotted as a function of temperature for 1 when R = SCH₃ and R¹ = Ph gave an calculated energy barrier ΔG₂₉₈ ^? of 17 kcal/mol. Similar studies for a variety of substituents R might be useful as a means of measuring relative steric bulk. At low temperature (ca. -50°C) broadening of the PPh, resonances began to appear indicating a second independent dynamic process thought to be slow rotation about the N-PPh₃ bond on the NMR time scale at that temperature.     

A Stereoselective Synthetic Route To (E)-α,β-Unsaturated Thioesters

Terminal alkynes 1 react with Cp₂Zr(H)Cl (Cp = η⁵-C₅H₅) and CO to give acylzirconocene chloride derivatives 2, which are trapped with arylsulfenyl chlorides to afford (E)-α,β-unsaturated thioesters.     

Theoretical study on the interactions of halogen‐bonds and pnicogen‐bonds in phosphine derivatives with Br2, BrCl,and BrF

The MP2 ab initio quantum chemistry methods were utilized to study the halogen‐bond and pnicogen‐bond system formed between PH₂X (X = Br, CH₃, OH, CN, NO₂, CF₃) and BrY (Y = Br, Cl, F). Calculated results show that all substituent can form halogen‐bond complexes while part substituent can form pnicogen‐bond complexes. Traditional, chlorine‐shared and ion‐pair halogen‐bonds complexes have been found with the different substituent X and Y. The halogen‐bonds are stronger than the related pnicogen‐bonds. For halogen‐bonds, strongly electronegative substituents which are connected to the Lewis acid can strengthen the bonds and significantly influenced the structures and properties of the compounds. In contrast, the substituents which connected to the Lewis bases can produce opposite effects. The interaction energies of halogen‐bonds are 2.56 to 32.06 kcal·mol^?1; The strongest halogen‐bond was found in the complex of PH₂OH???BrF. The interaction energies of pnicogen‐bonds are in the range 1.20 to 2.28 kcal·mol^?1; the strongest pnicogen‐bond was found in PH₂Br???Br₂ complex. The charge transfer of lp(P) ? σ*(Br? Y), lp(F) ? σ*(Br? P), and lp(Br) ? σ*(X? P) play important roles in the formation of the halogen‐bonds and pnicogen‐bonds, which lead to polarization of the monomers. The polarization caused by the halogen‐bond is more obvious than that by the pnicogen‐bond, resulting in that some halogen‐bonds having little covalent character. The symmetry adapted perturbation theory (SAPT) energy decomposition analysis showes that the halogen‐bond and pnicogen‐bond interactions are predominantly electrostatic and dispersion, respectively.     

Pyrolysis of Amino Acid Derived Stabilised Ylides as a Route to Chiral Acetylenic Amines and Amino Acids and Gaba Analogues

Abstract

We recently reported the pyrolysis of stabilised ylides as a method for overall conversion of carboxylic acids to homologous acetylenic esters and terminal alkynes.^1,2 This has now been applied successfully to amino acids. A wide range of alkoxycarbonyl protected amino acids have been converted to the stable crystalline ylides 1. These have been fully characterised, and upon FVP, eliminate Ph₃PO to afford the protected acetylenic amino acids 2 in good yield and without significant racemisation. Subsequent reactions of these extremely versatile intermediates have been used to gain access to a wide variety of chiral amine and amino acids of great interest as potential selective enzyme inhibitors and components for modified peptide structures.     

High-energy electron transfer dissociation (HE-ETD) using alkali metal targets for sequence analysis of post-translational peptides

Post-translational modifications (PTMs) of proteins are important in the activation, localization, and regulation of protein function in vivo. The usefulness of electron capture dissociation (ECD) and electron-transfer dissociation (ETD) in tandem mass spectrometry (MS/MS) using low-energy (LE) trap type mass spectrometer is associated with no loss of a labile PTM group regarding peptide and protein sequencing. The experimental results of high-energy (HE) collision induced dissociation (CID) using the Xe and Cs targets and LE-ETD were compared for doubly-phosphorylated peptides TGFLT(p)EY(p)VATR (1). Although HE-CID using the Xe target did not provide information on the amino acid sequence, HE-CID using the Cs target provided all the z-type ions without loss of the phosphate groups as a result of HE-ETD process, while LE-ETD using fluoranthene anion gave only z-type ions from z₅ to z₁₁. The difference in the results of HE-CID between the Xe and Cs targets demonstrated that HE-ETD process with the Cs target took place much more dominantly than collisional activation. The difference between HE-ETD using Cs targets and LE-ETD using the anion demonstrated that mass discrimination was much weaker in the high-energy process. HE-ETD was also applied to three other phosphopeptides YGGMHRQEX(p)VDC (2: X = S, 3: X = T, 4: X = Y). The HE-CID spectra of the doubly-protonated phosphopeptides (= [M + 2H]²⁺) of 2, 3, and 4 using the Cs target showed a very similar feature that the c-type ions from c₇ to c₁₁ and the z-type ions from z₇ to z₁₁ were formed via N-Cα bond cleavage without a loss of the phosphate group.     

Alternative Synthesis and Structures of C‐monoacetylenic Phosphaalkenes

An alternative synthesis of C‐monoacetylenic phosphaalkenes trans‐Mes*P=C(Me)(C≡CR) (Mes* = 2, 4, 6‐^tBu₃Ph, R = Ph, SiMe₃) from C‐bromophosphaalkenes cis‐Mes*P=C(Me)Br using standard Sonogashira coupling conditions is described. Crystallographic studies confirm cis‐trans isomerization of the P=C double bond during Pd‐catalyzed cross coupling, leading exclusively to trans‐acetylenic phosphaalkenes. Crystallographic studies of all synthesized compounds reveal the extend of π‐conjugation over the acetylene and P=C π‐systems.     

Metal complexes in organic chemistry,by R.P. Hougton. : Cambridge University Press,Cambridge - London - New York - Melbourne, 1979, vii + 308 pages, £21.00 (hard cover); £7.50 (paperback).

The reaction of acetic acid with (Ph₃P)₂Pt(dma) (dma = dimethylacetylene dicarboxylate), in the presence of triphenylphosphine, proceeds by addition of triphenylphosphonium acetate across the acetylenic triple bond, rather than by oxidative addition of the acid to platinum.     

Diarylcuprates for Selective Syntheses of Multifunctionalized Ketones from Thioesters under Mild Conditions

Ketones were selectively synthesized from thioesters by using diarylcuprates(I) generated in situ from copper(I) salts and aryl Grignard reagents in a 1 : 1.3–1.5 ratio under ambient temperature. During the ketone synthesis, various functional groups, such as carbonyl (ketones, esters, and amides), O-protecting groups, halogens, and heteroarenes, were tolerated to afford multifunctionalized ketones in excellent yields. This copper-mediated ketone synthesis could be applied to the synthesis of not only gluconolactone-derived ketone 6 , a synthetic intermediate in the transformation to the SGLT2 inhibitor canagliflozin, but also thiolactol 8 , a valuable synthetic intermediate for (+)-biotin. Control experiments on an isolated diphenylcuprate(I), [CuPh₂]⁻ ( 12 ), and DFT calculations revealed that this ketone synthesis proceeded by oxidative addition of the C−S bond of thioesters to [CuPh₂]⁻, while reductive elimination from the Cu^III intermediate produced the corresponding ketone and an inactive species [(RS)CuPh]⁻, the latter reacted with [CuPh]₄ ( 11 ) to regenerate the reactive diphenylcuprate(I).     

The molecular and electronic structure features of silatranes, germatranes, and their carbon analogs

Molecular geometries of fifty-six metallatranes N(CH₂CH₂Y)₃M-X and fifty-six carbon analogs HC(CH₂CH₂Y)₃M-X (M = Si, Ge; X = H, Me, OH, F; Y = CH₂, O, NH, NMe, NSiMe₃, PH, S) were optimized by the DFT method. Correlations between changes in the bond orbital populations, electron density ρ(r), electron density laplacian ∇²ρ(r), |λ₁|/λ₃ ratio, electronic energy density E(r), bond lengths, and displacement of the central atom from the plane of three equatorial substituents and the nature of substituents X and Y were studied. As the number of electronegative substituents at the central atom increases, the M←N, M-X, and M-Y bond lengths decrease, while the M←N bond strength and the electron density at critical points of the M←N, M-X, and M-Y bonds increase. An increase in electronegativity of a substituent (X or Y) is accompanied by a decrease in the ionicities of the other bonds (M-X, M-Y, and M←N) formed by the central atom (Si, Ge). A new molecular orbital diagram for bond formation is proposed, which takes into account the interaction of all five substituents at the central atom (M = Si, Ge) in atrane molecules. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 448–460, March, 2006.     

Predicting Stable Molecular Structures for (RNC)2AuIX Complexes

Calculations have been performed at the MP2 and DFT levels for investigating the reasons for the difficulties in synthesizing bis(isocyanide)gold(I) halide complexes. Three‐coordinated gold(I) complexes of the type (R₃P)₂Au^IX ( 1 ) can be synthesized, whereas the analogous isocyanide complexes (RNC)₂Au^IX ( 2 ) are not experimentally known. The molecular structures of (R₃P)₂Au^IX (X = Cl, Br, and I) and (RNC)₂Au^IX with X = halide, cyanide, nitrite, methylthiolate, and thiocyanate are compared and structural differences are discussed. Calculations of molecular properties elucidate which factors determine the strength of the gold‐ligand interactions in (RNC)₂Au^IX. The linear bonding mode of RNC favors a T‐shaped geometry instead of the planar Y‐shaped trigonal structure of (R₃P)₂Au^IX complexes that have been synthesized. An increased polarity of the Au–X bond in 2 leads to destabilization of the Y‐shaped structure. Chalcogen‐containing ligands or cyanide appear to be good X‐ligand candidates for synthesis of (RNC)₂Au^IX complexes.