A priori assessment of the stereoelectronic profile of phosphines and phosphites

This research has demonstrated the utility of a rigorously calibrated, molecular mechanics/semiempirical quantum mechanical protocol for developing stereoelectronic (Tolman) maps for phosphine ligands. A computational analysis of alkyl and aryl phosphines in common usage suggests that these ligands are quite similar stereoelectronically. A noticeable gap in the Tolman map for common phosphines is observed for large, electron-poor phosphines. Several candidates meeting these criteria were identified, the most promising of which is P(t-C(4)F(9))(3). Phosphines in which the phosphorus participates in a ring, which comprise a very small subset of reported phosphines, have very interesting stereoelectronic properties, particularly those in which the ligating phosphorus is part of a three-membered ring. In terms of steric properties, the symmetric deformation coordinate proposed by Orpen and co-workers on the basis of crystallographic studies is calculated with sufficient accuracy using PM3(tm) to allow good confidence in predictions of novel phosphines. For quantification of the electronic properties of phosphines, we analyzed changes in the CO stretching frequency upon changing the ancillary phosphine ligands.     

Synthesis and isomerism of methoxyallene derivatives of cymantrene

All of the three isomeric complexes possible for monosubstituted allenes were obtained by the interaction of 1-methoxypropadiene with CpMn(CO)₃ under UV irradiation or with CpMn(CO)₂(THF). The complexes were isolated as individual compounds and characterized by IR and¹H and¹³C NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1488–1490, August, 1994.     

Reaction of barbituric/thiobarbituric acid with phosphines or phosphites and dialkyl acetylenedicarboxylates for synthesis of phosphorus zwitterions or phosphonate derivatives

Abstract

A three-component reaction between barbituric/thiobarbituric acid, phosphines, and dialkyl acetylenedicarboxylates in dry acetonitrile led to the formation of barbiturate/thiobarbiturate-functionalized stable zwitterionic salts in a one-pot process. When trialkyl phosphites were used instead of phosphines, barbiturate/thiobarbiturate-functionalized phosphonates were obtained in good yields.     

Azinyl derivatives of ferrocene and cymantrene. Synthesis and properties

In the present review comparative data concerning various synthetic approaches and methodologies used in the series of ferrocene and cymantrene derivatives to create various materials, namely, catalytic systems, sensory and other molecular devices, polymers as well as physiologically active substances, for the period from 2000 till 2016 are given. Aspects of practical application of the above compounds are also considered.     

Evidence for the formation of isothiocyanate during sulfurisation of phosphines and phosphites using xanthane hydride

Contrary to a previous report, the sulfurisation of triphenylphosphines and trialkyl phosphites by 3-amino-1,2,4-dithiazole-5-thione (xanthane hydride) does not yield carbon disulfide and cyanamide as the additional reaction products but unstable thiocarbamoyl isothiocyanate which has been trapped with nucleophiles.     

Unsymmetrical secondary and tertiary phosphines and their derivatives

Conclusions Previously unknown secondary and tertiary phosphines with various functional groups have been obtained and described.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 414–415, February, 1967.     

Cyclic phosphites based on O-isopropylidene derivatives of D-mannitol

Russian Chemical Bulletin -     

Copper-catalyzed C-P bond construction via direct coupling of secondary phosphines and phosphites with aryl and vinyl halides

A general method for the coupling of aryl and vinyl halides with diaryl and dialkyl phosphines, as well as with dibutyl phosphite, is reported. This highly efficient transformation is realized through the use of copper(I) iodide as a catalyst, N,N'-dimethylethylenediamine as a ligand, and Cs(2)CO(3) as a base. A variety of sterically hindered and/or functionalized substrates were found to react under these reaction conditions to provide products in good to excellent yields. [reaction: see text]     

Theoretical study of the mechanism of nucleophilic substitution in cyclobutane derivatives

The mechanism of nucleophilic substitution in cyclobutane derivatives has been studied by means of ab initio molecular orbital computations on a model system. The results are in favour of a reaction which proceeds with inversion of configuration, in agreement with experimental data.     

Halogenophilic reaction of silylated phosphites with trichloroacetic acid derivatives

Silylated phosphites and amidophosphites react with trichloroacetonitrile and ethyl trichloroacetate with the formation of a P-Cl bond, which indicates a halogenophilic mechanism of the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 468–472, February, 1991.     

Selectivity tuning of cyclodextrin derivatives by specific substitution

A new, highly enantioselective cyclodextrin derivative combining the properties of heptakis(6‐O‐tert‐butyldimethylsilyl‐2,3‐di‐O‐methyl)‐β‐cyclodextrin and heptakis(2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin was prepared by exchanging a methyl group for an acetyl substituent in a single glucose unit of heptakis(6‐O‐tert‐butyldimethylsilyl‐2,3‐di‐O‐methyl)‐β‐cyclodextrin. A comparative evaluation of the separation capabilities showed that the enantioselectivity of both “parent” cyclodextrin derivatives is transferred to the new chiral stationary phase.     

Mechanism of the sulfurisation of phosphines and phosphites using 3-amino-1,2,4-dithiazole-5-thione (xanthane hydride)

Contrary to a previous report, the sulfurisation of phosphorus(III) derivatives by 3-amino-1,2,4-dithiazole-5-thione (xanthane hydride) does not yield carbon disulfide and cyanamide as the additional reaction products. The reaction of xanthane hydride with triphenyl phosphine or trimethyl phosphite yields triphenyl phosphine sulfide or trimethyl thiophosphate, respectively, and thiocarbamoyl isothiocyanate which has been trapped with nucleophiles. The reaction pathway involves initial nucleophilic attack of the phosphorus at sulfur next to the thiocarbonyl group of xanthane hydride followed by decomposition of the phosphonium intermediate formed to products. The Hammett rho-values for the sulfurisation of substituted triphenyl phosphines and triphenyl phosphites in acetonitrile are approximately -1.0. The entropies of activation are very negative (-114+/-15 J mol-1 K-1) with little dependence on solvent which is consistent with a bimolecular association step leading to the transition state. The negative values of DeltaS(not equal) and rho values indicate that the rate limiting step of the sulfurisation reaction is formation of the phosphonium ion intermediate which has an early transition state with little covalent bond formation. The site of nucleophilic attack has been also confirmed using computational calculations.     

The SRN2 mechanism of nucleophilic substitution

1-Alkylpyridiniums react with nitroalkane and ethylmalonate anions by a radical nucleophilic substitution mechanism not involving radical chains.     

Metal complexes with ligand-organic phosphites as polyolefin antioxidants. II. Kinetics and mechanism of synergism at oxidation inhibition by metal acetylacetonates and organic phosphites

The widely known synergism of oxidation inhibitors with metals of transient valency is shown in the new process with organic phosphite participation. The effects of inadditive strengthening phosphite action by acetylacetonates of transient metals (Me) have been investigated in different oxidation systems (solid polymer, melt, and liquid phase). The kinetic interpretation of effects, their quantitative analysis, and mathematical modeling are given, and the general regularities governing the efficiency of Me + organic phosphite compositions in any oxidation mode in the presence of initiator and at polymer autoxidation are revealed.