Sulphur-oxygen versus carbon-oxygen bond fission in the solvolysis of benzyl sulphenates

In contrast to p-anisyl trichloromethanesulphenate 1, which readily undergoes ethanolysis at room temperature with carbon-oxygen bond fission, the ethanolysis of the corresponding 2-nitrobenzenesulphenate 2 proceeds at a similar rate only at 100°, and involves sulphur-oxygen bond cleavage. While the solvolysis of 1 showed first-order kinetics, the solvolysis of 2 was second-order (first-order with respect to ester and to added base). The solvolysis rate of 2 decreases on going from 100% to 80% ethanol and by using pyridine instead of acetate as base, consistent with an S_N2 type mechanism involving nucleophilic displacement at sulphur by the base or lyate ion. The rate of solvolysis of 1 is greatly enhanced in polar solvents and correlates satisfactorily with the ionization of p-methoxyneophyl tosylate. An ionization mechanism to some ion pair species is suggested for the solvolysis of 1.     

THE SYNTHESIS,SOLVOLYSIS AND REARRANGEMENT OF BENZYL TRIFLUOROMETHANESULFINATES

Abstract

The synthesis and reactivity of benzyl trifluoromethanesulfinates have been investigated. These esters are easily and almost quantitatively obtained by selective oxidation of the corresponding sulfenates. A study of their behavior has revealed some unique features. In sharp contrast to benzyl arenesulfinates, which undergo ethanolysis with complete sulfur-oxygen bond fission, the corresponding trifluorornethanesulfinates undergo ethanolysis with exclusive carbon-oxygen bond fission, and with a rate enhancement by a factor of 6 powers of ten. The unusual high reactivity of these esters, comparable to that of the corresponding tosylates, is discussed. A kinetic study of the solvent and substituent effects on the rate of solvolysis has been performed. Also in contrast with benzyl arenesulfinates, these esters undergo facile rearrangement to sulfone on heating in polar nonhydroxylic solvents such as acetonitrile, in high yields. The mechanisms of solvolysis and rearrangement are discussed.     

DIALKYL THIOPHOSPHONATE DERIVATIVES OF TRIORGANOTIN(IV)

Abstract

The reaction of triorganotin chlorides with sodium dialkyl thiophosphites proceeds to completion on refluxing the reactants in a 1:1 molar ratio for about ten hours. Similar reactions of triorganotin chloride with dialkyl thiophosphonate do not give comparable yields in the presence of triethylamine. The products formed are colorless volatile liquids having pungent odour, are miscible with common organic solvents and are found to be monomeric. Exposure of these compounds to atmospheric oxygen the thiophosphite [Sn-S-P] linkage was oxidized to a thiophosphate [Sn-O-P(S)] linkage. These complexes have been characterized by elemental analyses, molecular weight determination, IR, ¹H NMR and ³¹P NMR spectral data.     

OXIDATIVELY-INDUCED FORMATION OF DIALKYL HYDROGENPHOSPHONATES FROM PHOSPHOROTHIONATES

Abstract

Peracid oxidation of triester and related phosphorothionates and diester phosphorothioic acids with excess magnesium monoperoxyphthalate in water gives, among other products, dialkyl hydrogenphos-phonates in yields of up to 70%. Hydrogenphosphonate formation is facilitated by the presence of a good leaving group in the starting material.     

HIGHLY STEREOSELECTIVE SYNTHESIS OF DIALKYL 2-ALKYLIDENE GLUTARATES

Nucleophelic substitution of dialkyl (E)-2-bromomethylene glutarates 2 by magnesium dialkyl cuprates generated in situ provided a regio and highly stereoselective methodology for the synthesis of dialkyl 2-alkylidene glutarates 3 in good yields.     

MIXED HALIDE DIALKYL AND ALKYLENEDITHIOPHOSPHATE DERIVATIVES OF RUTHENIUM (III)

Abstract

Mixed chloride dialkyl and alkylenedithiophosphates of ruthenium (III). RuC1_3-n|(S₂P(OR)₂|n (R = Prⁿ, and Ph) and RuCl_3-n,[S₂ POGO]n G =-CMe₂CMe₂,- CH₂CMe₂CH₂-, -CH₂CEt₂CH₂-. and -CMe₂CH₂CHMe-, n = 1,2 have been synthesized for the first time by the reactions of ruthenium trichloride with ammonium dialkyl and alkylenedithiophosphate or alternatively by disproportionation reactions of ruthenium trichloride with ruthenium tris(dialkyl and alkylenedithiophosphates) in different stoichiometric ratios in benzene.

These new complexes have been characterized by elemental analysis, molecular weight determinations, as well as IR and NMR (¹H and ³¹P) data. Chelated structures with bidentate dialkyl and alkylenedithiophosphates groups have been proposed for all these derivatives.     

Solvolyses of diarylmethyl chlorides. A comprehensive stability scale for diarylcarbenium ions.

Eleven donor substituted diarylmethyl chlorides have been solvolyzed in ethanol. The rate constants, determined at 25°C, and additional ethanolysis data taken from the literature have been connected with solvolvsis rate constants, determined in other solvents, to construct a stability scale for 74 diarylcarbenium ions, covering a rate range of > 10¹². Correlation equations are given which allow the calculation of solvolysis rates in other solvents, of equilibrium constants, and of rate constants for reactions involving diarylcarbenium ions.     

Formation of Dialkyl 2‐[3‐Alkoxy‐1‐(alkylimino)‐1‐chloro‐3‐oxopropan‐2‐ylidene]hydrazine‐1,1‐dicarboxylates of α‐(Alkoxycarbonyl)imidoyl Chlorides from PhosphineDiazo Ester Zwitterions and Nef‐Isocyanide Adducts

A novel transformation involving phosphine? diazo ester zwitterions (generated from dialkyl azodicarboxylates with Ph₃P) and α‐(alkoxycarbonyl)imidoyl chlorides (prepared from α‐addition of acyl chlorides to alkyl isocyanides) to afford dialkyl 2‐[3‐alkoxy‐1‐(alkylimino)‐1‐chloro‐3‐oxopropan‐2‐ylidene]hydrazine‐1,1‐dicarboxylates in moderate yields, is described.     

反丁烯二酸酯的自由基共聚反应

<正> 对反丁烯二酸酯(DRPs)类单休的均实反应研究已有许多报道。研究结果表明,所有的正烷基酯基DRFs单体,如反丁烯二酸二王丙酯等,均表现出很低的聚合反应活性,因而得不到高分子量的均聚物;而某些非正烷基酯的DRFs单体,如反丁烯二酸二异丙酯则显示出很高的聚合反应活性并可形成高分子量的聚合物。对反丁烯二酸酯同其他乙烯类单体(如苯乙烯等)的共聚研究曾有一些报道,但对DRFs单体之间的共聚     

Unprecedented base effect on the synthesis of chiral phosphinate esters: A new route to P-chiral phosphine oxides of high enantiomeric purity

The stereochemical outcome of the reaction of chiral secondary alcohols with a phosphinyl chloride was found to be highly dependent on the achiral base used. Thus, the reaction of the readily available sugar derived carbinols, 1 and 2, with methylphenylphosphinyl chloride in the presence of triethylamine yields stereoselectively the corresponding Snp-phosphinates 3Sp and 5Sp in 94 and 92% diastereomeric excess (de). Simply changing the base from triethylamine to pyridine affords Rp-phosphinates 4Rp and 6Rp epimers to 3Sp and 5Sp at the phosphinyl phosphorus in 50 and 40% de respectively. These phosphinate esters were found to be good P-chiral transferring intermediates, they react with Grignard reagents under very mild conditions to give the corresponding phosphine oxides. Both enantiomers Sp- and Rp-o-anisylmethylphenylphosphine oxide (PAMPO) as well Sp- and Rp- methylphenylpropyl phosphine oxide were obained enantiomerically pure in high yields     

S(N)2 Mechanism for Alcoholysis, Aminolysis, and Hydrolysis of Acetyl Chloride

First-order solvolysis rate constants are reported for solvolyses of acetyl chloride in methanol and MeOD, and in binary aqueous mixtures with acetone, acetonitrile, ethanol, methanol, and trifluoroethanol at 0 degrees C. Product selectivities (S = [MeCOOR]/[MeCOOH] x [water]/[alcohol]) are reported for solvolyses in ethanol/ and methanol/water at 0 degrees C. Solvolyses of acetyl chloride show a high sensitivity to changes in solvent ionizing power, consistent with C-Cl bond cleavage. As the solvent is varied from pure ethanol (or methanol) to water, S values and rate-rate profiles show no evidence for the change in reaction channel observed for solvolyses of benzoyl and trimethylacetyl chlorides. However, using rate ratios in 40% ethanol/water and 97% trifluoroethanol/water (solvents of similar ionizing power but different nucleophilicities) to compare sensitivities to nucleophilic attack, solvolyses of acetyl chloride are over 20-fold more sensitive to nucleophilic attack than benzoyl chloride. The solvent isotope effect of 1.29 (MeOH/MeOD) for acetyl chloride is similar to that for p-methoxybenzoyl chloride (1.22) and is lower than for benzoyl chloride (1.55). Second-order rate constants for aminolyses of acetyl chloride with m-nitroaniline in methanol at 0 degrees C show that acetyl chloride behaves similarly to p-methoxybenzoyl chloride, whereas benzoyl chloride is 40-fold more sensitive to the added amine. The results indicate mechanistic differences between solvolyses of acetyl and benzoyl chlorides, and an S(N)2 mechanism is proposed for solvolyses and aminolyses by m-nitroaniline of acetyl chloride (i.e. these reactions are probably not carbonyl additions, but a strong sensitivity to nucleophilic attack accounts for their high rates).     

Simple,Novel Synthesis for 1-Carbamoyl-lH-benzotriazole and Some of Its Analogs

1-Carbamoyl-1H-benzotriazole (benzotriazole-1-carboxamide, 2a), an effective carbamoyl chloride substitute, and a range of its analogs can be synthesized in good yields in two very simple steps from 1,2-diaminobenzene. The facile preparation of the intermediate o-aminophenylurea is key to this process. A preliminary study of the reactivity of 2a has shown that once in solution in tetrahydrofuran (THF), the 1-carbamoyl isomer equilibrates to give a mixture of both 1- and 2-isomers. If the solvent is ethanol or water, equilibration occurs rapidly compared to the ultimate formation of solvolysis products.     

Enzyme-like acceleration for the hydrolysis of a DNA model promoted by a dinuclear Zn(II) catalyst in dilute aqueous ethanol

The rates and products of cleavage of methyl (2-chloro-4-nitrophenyl) phosphate (2) promoted by a dinuclear Zn(II) complex (3) of 1,3-bis-N,N'(1,5,9-triazacyclododecyl)propane along with 1 equiv of ethoxide were investigated in ethanol solution containing small amounts of water (8 mM or=1.6 x 10(17) times relative to the background hydroxide reaction, suggesting that complex 3 promotes the hydrolysis at least 1000 times more effectively than ethanolysis.     

NEW SYNTHETIC ROUTE TO DIALKYLPHOSPHINIC ACIDS

Abstract

The dialkylphosphinic acids, 5a-5e, can be obtained by reacting bis(trimethylsiloxy)phosphine with the highly reactive alkyl halides, 2a-2e, in the presence of chlorotrimethylsilane and triethylamine, followed by ethanolysis of the resulting trimethylsilyl dialkylphosphinates, 4a-4e.     

Is the tert-butyl chloride solvolysis the most misunderstood reaction in organic chemistry? Evidence against nucleophilic solvent participation in the tert-butyl chloride transition state and for increased hydrogen bond donation to the 1-adamantyl chloride solvolysis transition state.

Despite theoretical calculations to the contrary, it has been argued that the 1-adamantyl cation is more stable than the tert-butyl cation in media of high dielectric constant. This argument has been utilized to suggest that the higher rate of solvolysis of tert-butyl chloride in aqueous ethanol is evidence for nucleophilic solvent participation in this classic reaction. Further, in "more highly ionizing" solvents, the rate of 1-adamantyl chloride is nearly the same as that of tert-butyl chloride, which is interpreted as a manifestation of the relative stabilities of the cations. However, the evidence cited does not explain the increased sensitivity of the rate of solvolysis of 1-adamantyl chloride over tert-butyl chloride to solvents which are better able to donate hydrogen bonds. The hypothesis developed here is that 1-adamantyl chloride solvolysis is assisted by hydrogen bond donation departing chloride ion to a greater extent than that of tert-butyl chloride solvolysis, most likely due to lessened steric interactions in a developing pyramidal cation. This hypothesis is supported by multiparameter solvent effect factor analyses utilizing the KOMPH2 equation which, in addition, quantifies the important role of ground-state destabilization due to strong solvent-solvent interactions. An important result from the good correlation of free energies of transfer of the tert-butyl chloride solvolysis transition state is that there is no change in mechanism, and, in particular, no nucleophilic participation even in non-hydroxylic basic solvents. The equation is also applied to the case of dimethylsulfonium ion solvolyses where the tert-butyl salt reacts substantially faster than the 1-adamantyl salt in ethanol and the gas phase. The decreased rate of the former in hydrogen bond donating solvents relative to the gas phase is as yet unclear. Solvent N values that were generated to characterize solvent nucleophilicity are shown not to be correlated by measures of solvent basicity but rather by the negative of measures of solvent hydrogen bond donor ability.     

Organophosphorus chemistry. Part 21 [1]. Insertion of olefins into P  CF3 bonds

Tris(trifluoromethyl)phosphine and ethylene reacted efficiently under u.v. irradiation to give 3,3,3-trifluoropropylbis(trifuomothyl) phosphine in good yield. With vinyl fluoride, vinylidene fluoride, and propene the reaction was regioselective rather than regiospecific, and the yield of 1:1 adduct was low. In these reactions, and in those with vinyl chloride, but-1-ene, and hexafluoropropene, in which only traces of 1:1-adduct could be detected, the bulk of the olefin and of the phosphine was recovered, and numerous by-products consistent with radical intermediates were identified. With propyne, 1,1,1-trifluoro-3-bis(trifluoromethyl)phosphino-cis-but-2-ene was obtained in moderate yield, but no reaction occurred between the phosphine and either but-2-yne or hexafluorcbut-2-yne. Tris(trifluoromethyl)phosphine oxide did not form an adduct with ethylene, tetrafluoroethylene, or propyne.Bis(trifluoromethyl)phosphine and dimethylphosphine both reacted readily under u.v. irradiation with 3,3,3-trifluoropropene, the phosphinyl radical attacking the terminal carbon in each case.     

Kinetic study of a complex triangular reaction system in alkaline aqueous-ethanol medium using on-line transmission FTIR spectroscopy and BTEM analysis

The kinetics of the base-catalyzed reaction of methyl 4-hydroxybenzoate in aqueous-ethanol solvent medium was studied and analyzed via combined on-line transmission FTIR spectroscopy and Band-Target Entropy Minimization (BTEM) technique. This reaction is considered complex since it involves simultaneous hydrolysis and ethanolysis reactions of methyl 4-hydrozybenzoate (MP) to form ethyl 4-hydroxybenzoate (EP) as an intermediate and sodium 4-hydroxybenzoate as a final product. The pure component spectra of the reactive species involved in the reaction were reconstructed using BTEM technique. Their corresponding real concentrations were calculated and subsequently used for analyzing the kinetics of this triangular reaction system. The effects of temperature and solvent mixture compositions were studied. In general, the results show that the rates of both hydrolysis and ethanolysis reactions increase with temperature. Addition of ethanol to the solvent mixture also reduces the rates of the hydrolysis reactions. The effect of solvent mixture on the rate of ethanolysis reaction is more complex and influenced by at least two competing factors, namely the concentration of ethoxide ion in the solution and the stabilization effect on the reactant. The enthalpy and entropy activation parameters, ΔH^‡ and ΔS^‡, of both the hydrolysis and ethanolysis reactions were determined using the Eyring equation and the activation parameters confirm the associative nature in the elementary steps in these reactions. Finally, it is shown that the dominant synthetic pathway in this triangular system changes from direct hydrolysis of methyl 4-hydrozybenzoate to the indirect pathway via ethanolysis and then hydrolysis depending on the solvent mixture composition.     

Rhodium catalyzed asymmetric synthesis of Chiraphos derivatives

Herein, we report a highly efficient versatile synthetic route to Chiraphos derivatives through Rh/Ph-bod catalyzed asymmetric addition of aryl boronic acids to phosphinyl dienes. Various substituted phosphinyl dienes, both on the parent skeleton and the phosphine atoms, were well tolerated with this method and provided chiral phosphine oxides in satisfied yield and up to 95% ee. The corresponding Chiraphos derivative displayed an advantage over Chiraphos in the representative Pd-catalyzed asymmetric 1,4-addition reaction.     

Intramolecular cyclization of dialkyl[2-(5-chloro-2-hydroxyphenyl)-2-phenylethenyl]phosphine oxides by the action of thionyl chloride

An efficient procedure has been proposed for the synthesis of quasiphosphonium salts, 2,2-dialkyl-6-chloro-4-phenyl-2H-1,2-benzoxaphosphinin-2-onium chlorides, via cyclization of dialkyl[2-(5-chloro-2-hydroxyphenyl)-2-phenylethenyl]phosphine oxides under the action of thionyl chloride.     

Application of an electroneutral phosphine ligand to organo-platinum chemistry: Pentafluoroethyldiphenylphosphine (pfepp)

The synthesis, characterization and molecular structures of two platinum complexes bearing the novel phosphine pentafluoroethyldiphenylphosphine (pfepp; 1) is reported. pfepp is a sterically bulky, electronically neutral phosphine ligand. Treatment of (cod)PtMe₂ with two equivalents of pfepp yields cis-(pfepp)₂PtMe₂ 2. Addition of one equivalent of acetyl chloride to a methanol/dichloromethane solution of 2 results in the formation of trans-(pfepp)₂PtMeCl 3. Complexes 2 and 3 were characterized by IR, multinuclear NMR and elemental analysis. The X-ray crystal structures of 2 and 3 are also reported and confirm the geometry assignments around the metal center.