Showing papers in "Phosphorus Sulfur and Silicon and The Related Elements in 1994"
TL;DR: In this paper, the authors summarized data available in literature on asymmetric synthesis of phosphorus analogs of amino acids and arranged them according to the type of bond formation during a chiral center creation.
Abstract: Data available in literature on asymmetric synthesis of phosphorus analogs of amino acids are summarized. The methods described are arranged according to the type of bond formation during a chiral center creation. The asymmetric synthesis was shown to be in dynamic development and can be considered as a valuable approach for production of optically active phosphorus analogs of amino acids.
118 citations
TL;DR: Thiols were oxidized by Cu(II) in a reaction that had two phases; the second phase was much slower for glutathione (GSH) than it was for cysteine and accounts for previous reports that GSH is oxidized at a slower rate than Cysteine.
Abstract: Thiols were oxidized by Cu(II) in a reaction that had two phases. There was an immediate reaction between thiol and Cu(II) with loss of thiol, measured by its reaction with 5,5′-dithio-bis(2-nitrobenzoic acid), and formation of Cu(I), measured by its reaction with bathocuproinedisulfonic acid. With equal molar concentrations of thiols and Cu(II), only the first phase was observed and thiols were oxidized in less than 15 sec. When the concentration of Cu(II) was limiting (200 μM thiol and 10 to 160 μM Cu(II)), the second phase of the reaction was observed; this phase was much slower for glutathione (GSH) than it was for cysteine and accounts for previous reports that GSH is oxidized by Cu(II) at a slower rate than cysteine. It is proposed that Cu(II) reacts with thiols to form Cu(II)-thiol complexes, Cu(II) is reduced to Cu(I), and the thiols are oxidized to the corresponding radicals. Two of the radicals react to form a disulfide and Cu(I) reacts with a second thiol to form a Cu(I)-thiol complex ...
70 citations
TL;DR: In this paper, a highly selective thioselenation of olefins was achieved by using a disulfide-diselenide mixed system, which was obtained by using disentangled disentangles.
Abstract: A highly selective thioselenation of olefins has been attained by using a disulfide-diselenide mixed system.
67 citations
TL;DR: The study of phosphorus analogues of the natural a-amino acids has accelerated in the past fifteen years, not least due to the finding of molecules with useful biological activity as mentioned in this paper.
Abstract: The study of phosphorus analogues of the natural a-amino acids has accelerated in the past fifteen years, not least due to the finding of molecules with useful biological activity Our knowledge in this area has been summarized in several recent review articles1-5 Furthermore aminophosphonic acids find increasing use as a tool in investigating the metabolism of natural amino acids6 The family of 1-aminoalkylphosphonic acids has been most studied and to date analogues of all the common protein amino acids have been described in the literature
62 citations
TL;DR: In this paper, it was shown that cycloaddition of cyclodimers and iminoboranes yields cyclotrimers, which can be formed irreversibly from cyclobutadienes.
Abstract: Iminoboranes RB [tbnd] NR′, isoelectronic with alkynes, cyclooligomerize to give B-N rings (RBNR′)n that are either analogues of cyclobutadienes (n = 2) or benzenes or Dewar benzenes (n = 3) or cyclooctatetraenes (n = 4), depending on the ligand set R/R′ and on conducting the oligomerization either thermally or catalytically. Cyclodimers and cyclotetramers may either undergo reversible interconversions or cyclotetramers are formed irreversibly from cyclodimers. The (4+2) cycloaddition of cyclodimers and iminoboranes yields cyclotrimers. Cyclotrimers may thermally be converted into cyclodimers, and poly(iminoboranes), isoelectronic with polyalkynes, can thermally be depolymerized into cyclotrimers. nido-Cluster derivatives of N2B4H6, arachno-cluster derivatives of N2B3H7, four-membered rings N2B2R3R′, or five-membered rings N2B3R4R′ are isolated, when three-membered rings NB2R3, isoelectronic with cyclopropenyl cations, either dimerize or add aminoboranes H2B=NR′2 or insert nitrenes R′N (from R′N3...
55 citations
TL;DR: In this paper, aspects of the coordination chemistry of antimony and bismuth trihalides and phenyl bismith dihalides with phosphine and ether ligands are discussed together with a description of the bonding in these complexes.
Abstract: Aspects of the coordination chemistry of antimony and bismuth trihalides and phenyl bismuth dihalides with phosphine and ether ligands are discussed together with a description of the bonding in these complexes. The bonding model described provides a rationalisation of the coordination geometries and the observed trends in some of the bond lengths and angles.
34 citations
TL;DR: In this article, a mixture of N-chlorosuccinimide, triphenylphosphine and sodium azide is used to form acyl azides in high yields.
Abstract: Carboxylic acids react with a mixture of N-chlorosuccinimide, triphenylphosphine and sodium azide at -30°C to form acyl azides in high yields. When two equivalents of triphenylphosphine are applied and the temperature allowed to raise, the reaction yields directly α-carbonyl stabilized iminophosphoranes via Staudinger reaction of the phosphine with the intermediate acyl azide.
33 citations
TL;DR: The effect of counterion on the structure of several anionic metal-chalcogenide complexes is discussed in this paper, and some conclusions are made regarding our ability to predict the dimensionality of a structure.
Abstract: The effect of counterion on the structure of several anionic metal-chalcogenide complexes is discussed. Examples of compounds which show these dramatic effects are presented and some conclusions are made regarding our ability to predict the dimensionality of a structure.
33 citations
TL;DR: In this paper, two α-substituted aminomethyl phosphonates have been synthesized and reaction conditions are discussed, and all the products have been confirmed by 1H NMR, IR spectra and elemental analysis, and x-ray diffraction.
Abstract: Two series of novel α-substituted aminomethyl phosphonates (1) and (2) have been synthesized and the reaction conditions are discussed. All the products have been confirmed by 1H NMR, IR spectra and elemental analysis, and x-ray diffraction. The bioassay showed that some of the compounds inhibit the growth of the leukemia L1210 cell in vitro.
29 citations
TL;DR: The synthetic, spectroscopic and biological studies of some diorganosilicon(IV) complexes derived from fluoroimines having NS and NO donor systems have been undertaken as discussed by the authors.
Abstract: The synthetic, spectroscopic and biological studies of some diorganosilicon(IV) complexes derived from fluoroimines having NS and NO donor systems have been undertaken. The fluoroimines were prepared by the condensation of 2-Fluorobenzaldehyde and 1-(2-Fluorophenyl)-ethanone with hydrazinecarbothioamide and hydrazinecarboxamide. These imines, on interaction with diorganosilicon(IV) chlorides, yield complexes having Si—S/Si—O and Si→N bonds. The structures of these compounds have been elucidated by microestimations and spectral [(UV), (IR), (proton-1, carbon-13, fluorine-19 and silicon-29 NMR)] studies which unerringly point to a trigonal bipyramidal and octahedral geometries for unimolar and bimolar reactions, respectively, around silicon(IV), as the active lone pair of nitrogen is also included in the coordination sphere. Studies were conducted to assess the comparative growth inhibiting potential of the synthesized complexes against the fluoroimines for a variety of fungal and bacterial strains...
29 citations
TL;DR: In this article, the structural data on P-N compounds and their complexes and ab initio molecular orbital calculations on selected model systems provide strong evidence for negative hyperconjugation as a dominant feature of multiple bonding between phosphorus and nitrogen.
Abstract: Synthetic, spectroscopic and X-ray structural studies on linear and cyclic λ3-diphosphazanes, λ3-cyclotriphosphazanes, λ5-cyclotriphosphazenes and a bicyclic P4N5 derivative are summarised. Transition metal organometallic chemistry of linear and cyclic λ3-phosphazanes and suitably functionalised λ5-cyclotriphosphazenes is also investigated. Novel mono- and dinuclear palladium complexes have been isolated from spirocyclic λ5cyclotriphosphazenes by facile hydrolytic cleavage of a λ5-diazaphospholane ring. The structural data on P-N compounds and their complexes and ab initio molecular orbital calculations on selected model systems provide strong evidence for “negative hyperconjugation” as a dominant feature of multiple bonding between phosphorus and nitrogen.
TL;DR: The multi-sulfur donor ligand 1,3dithole-2-one-4,5-dithiolate (DMID) has been prepared as discussed by the authors.
Abstract: The multi-sulfur donor ligand 1,3-dithole-2-one-4,5-dithiolate (DMID) has been prepared. Monoanionic or dianionic or non-integer oxidation state complexes of DMID with Ni(II), Cu(II) and Zn(II) have been isolated as the tetrabutylammonium (TBA), tetraethylammonium (TEA), or tetramethylammonium (TMA) salts. Elemental analyses give good results for all the compounds. In addition, the compounds are also characterized by negative ion Fast Atom Bombardment (FAB) mass spectral analysis, Fourier Transform Infrared spectral (FT-IR) analysis, UV-Vis spectral analysis and Cyclic voltammetry. Their electrochemical properties are studied.
TL;DR: The tetramethylguanidinyl-substituted phosphines 3a-3c and 4a-4d were prepared by reaction of N,N,N′, N′-tetramethyl guanidine 1 (TMG) or N-trimethylsilyl-N′.
Abstract: The tetramethylguanidinyl-substituted phosphines 3a–3c and 4a–4d were prepared by reaction of N,N,N′,N′-tetramethylguanidine 1 (TMG) or N-trimethylsilyl-N′,N′,N′,N″-tetramethylguanidine 2 with RPCl...
TL;DR: In this article, the mono-lithium derivatives of the silylamines R(CMe3)2SiNH2 form dimers, and a trisilazane is obtained as a byproduct.
Abstract: The mono-lithium derivatives of the silylamines R(CMe3)2SiNH2 form dimers [R(CMe3)2SiNHLi[sdot]TMEDA]2 (R = Ph (1), Me(2)). 1 and 2 react with (CMe3)2SiF2 to give R(CMe3)2Si—NH—Si(CMe3)2F (R = Ph (3), R = Me (4). A trisilazane 6 (R = Ph) is obtained as a by-product. Ph(CMe3)2Si—NH—Si(CMe3)2Ph (5) is formed in the reaction of 1 with Ph(CMe3)2SiF. The lithium derivative of 3 crystallizes from thf as a momomeric LiF-adduct of an iminosilane (Ph(CMe3)2Si—N=Si(CMe3)2FLi(thf)3, 7). In the presence of tmeda a salt like amid is isolated ([Ph(CMe3)2SiNSi(CMe3)2F]⊝-Li(tmeda)2]⊕, 8). The lithium derivative of 4 forms a dimer ([Me(CMe3)2SiNLi-FSi(CMe3)2]2, 9) associated via Li—F contacts. 9 adds tmeda with formation of Me(CMe3)2SiNLi(tmeda)Si(CMe3)2F (10). In 12-crown-4 the salt [Me(CMe3)2SiNSiF(CMe3)2]⊝[Li(12-crown-4)2]⊕ (11) results from 9. 7 reacts with Me3SiCl in the presence of thf by a fluorine/chlorine exchange. The free iminosilane 12 is thus obtained. The crystal structures of 7, 8 and 9 have been d...
TL;DR: In this article, the crystal structure of Li(thf)PHCy (thf = tetrahydrofuran, Cy = cyclohexyl) shows a polymeric structure with five-coordinate phosphorus atoms and fourcoordinate lithium atoms.
Abstract: The crystal structure of Li(thf)PHCy (thf = tetrahydrofuran, Cy = cyclohexyl) shows a polymeric structure with five-coordinate phosphorus atoms and four-coordinate lithium atoms. Three different Li-P distances are observed, which range from 2.608(8) to 2.631(8) A.
TL;DR: In this paper, 2-nitropentachlorobutadione (2-NT) was obtained by the reaction of compound 1 with thiols in EtOH containing sodium hydroxide.
Abstract: 2-Nitropentachlorobutadione (1) gives 3a–b, 3d and 4c by the reaction with thiols in DMF containing triethylamine. 5a–b, 6c and 6d are prepared by the reaction of compound 1 with thiols in EtOH containing sodium hydroxide. 7c and 7d are formed by the reaction of compound 1 with thiols in the absence of a solvent. Poly(thio)substituted compounds (8, 10, 12) have been oxidized by 3-chloroperbenzoic acid (m-CPBA) in chloroform at 0°C. 9a, b and c sulfonyl compounds have been obtained from 8a, b, c and m-CPBA. Compound 13a containing sulfone and sulfoxide groups was prepared from compound 12a by oxidation under the same conditions. Sulfinyl compounds 10a, b, c give compounds 11a, b, c by reaction with m-CPBA.
TL;DR: In this article, the electronic structure of various substituted title compounds has been investigated by ab initio (3−21G∗) and MNDO molecular orbital calculations, and the preference for the cis or trans isomers can be traced in the behavior of the HOMO of the parent cyclodiphosphazane under the influence of the ring substituents.
Abstract: The electronic structure of various substituted title compounds has been investigated by ab initio (3–21G∗) and MNDO molecular orbital calculations. The preference for the cis or trans isomers can be traced in the behavior of the HOMO of the parent cyclodiphosphazane under the influence of the ring substituents. Thus, alkyl groups promote folding of the ring and tend to occupy the cis positions on phosphorus, while aryl groups at nitrogen make the ring planar and orient the substituents on phosphorus to the trans positions. In case of electron pair bearing substituents the conformation is determined by a more subtle interplay of their donor acceptor properties.
TL;DR: Esters can be generated directly in good yields under mild conditions from the corresponding carboxylic acid and alcohol in the presence of equivalent amounts of pyridine, triphenylphosphine and N-halo-succinimide as discussed by the authors.
Abstract: Esters can be generated directly in good yields under mild conditions from the corresponding carboxylic acid and alcohol in the presence of equivalent amounts of pyridine, triphenylphosphine and N-halo-succinimide.
TL;DR: The title compounds (4a-f) were prepared by s-alkylation of 4-cyano-5,6-difur-2′-yl-2H-pyridazine-3-thione and subsequent cyclization in ethanol in the presence of potassium carbonate as discussed by the authors.
Abstract: The title compounds (4a-f) were prepared by S-alkylation of 4-cyano-5,6-difur-2′-yl-2H-pyridazine-3-thione (2) and subsequent cyclization in ethanol in the presence of potassium carbonate. Reaction of o-disubstituted thienopyridazines (4a-d) with different reagents afforded tricyclic compounds namely, imidazothienopyridazine (5), pyridazinothienooxazine (6) and pyridazinothienopyrimidines (7–9). Most of the prepared compounds exhibited pronounced antibacterial activity.
TL;DR: In this paper, the synthesis, characterization, and reactions of octasilacubane Si8R8 (R = 2,6-diethylphenyl), octagermacubane Ge6R6 (R= 2.6-diisopropyl phenyl), hexasilaprismane Si6-R6, and hexagermaprismanes Ge6r6 are reported.
Abstract: Syntheses, characterization, and reactions of octasilacubane Si8R8 (R = 2,6-diethylphenyl), octagermacubane Ge8R8 (R = 2,6-diethylphenyl), hexasilaprismane Si6R6 (R = 2,6-diisopropylphenyl), and hexagermaprismane Ge6R6 (R = 2,6-diisopropylphenyl) are reported.
TL;DR: In this article, a two-step procedure was used to combine equimolar amounts of fluorinated benzaldehydes and anilines to benzaldehyde-(N-aryl-)imines to obtain N-arylamino-arylmethanephosphonic acid diethylesters.
Abstract: Fluorinated α-C-and N-arylsubstituted aminomethanephosphonic acid diethylesters 5 are prepared in high yields by a „two-step“ procedure: mixing equimolar amounts of fluorinated benzaldehydes 1 and anilines 2 to benzaldehyde-(N-aryl-)imines 3. Subsequently N-arylamino-arylmethanephosphonic acid diethylesters 5 are obtained by addition of diethyl phosphite 4 to the imines 3. All compounds are characterized by 31 P {1 H}, 1H and 19F NMR spectroscopical investigations. External biological studies involving the 27 new aminophosphonic acid esters 5 show insecticidal activity of N-4-trifluoromethoxy-phenylamino-phenylmethanephosphonic acid diethylester 5h towards harmful and parasitic insects.
TL;DR: Boron analogues of a variety of biologically important molecules have been synthesized and characterized and exhibit potent biological activity and possess a wide variety of pharmacological behavior such as hypolipidemic, anticancer, anti-inflammatory,Anti-osteoporosis, and other activity in animal model studies.
Abstract: Boron analogues of a variety of biologically important molecules have been synthesized and characterized. Analogues of amino acids, peptides, phosphonates, nucleosides, nucleic acids, and other derivatives, all containing 4-coordinate boron, possess sufficient hydrolytic and oxidative stability to be useful under physiological conditions. Bearing close structural resemblance to their natural organic counterparts (but different charge), the boron analogues exhibit potent biological activity and possess a wide variety of pharmacological behavior such as hypolipidemic, anticancer, anti-inflammatory, anti-osteoporosis, and other activity in animal model studies. Boron analogues may also be useful in boron neutron capture therapy for the treatment of cancer. Other applications to medical diagnostics exist.
TL;DR: In this paper, the Wittig-Horner reagents were used with o-quinone diimine to give the respective phosphonate adducts and the alkylated product.
Abstract: Wittig-Horner reagents (1a–c) react with o-quinone diimine (2a) to give the respective phosphonate adducts (3a–c) and the alkylated product 4. The reaction of p-quinone diimine (2b) with the same reagents yield adducts 5, 6 and 7, respectively. Structural reasoning for the new compounds was based on compatible analytical and spectral data. The mechanism that accounts for formation of adducts 3 is illustrated in Scheme 2.
TL;DR: In this paper, the α-oxoketene dithioacetals of general formula 1 (Scheme 2), undergo regioselective 1,2-addition with allyl anions to afford the corresponding carbinol acetals 6 in quantitative yields, which on treatment with BF3.Et2O in refluxing benzene yield the corresponding aromatic systems.
Abstract: The α-oxoketene dithioacetals of general formula 1 (Scheme 2), undergo regioselective 1,2-addition with allyl anions to afford the corresponding carbinol acetals 6 in quantitative yields, which on treatment with BF3.Et2O in refluxing benzene yield the corresponding aromatic systems. The method has been shown to be widely applicable as exemplified by a large number of allyl anions (Scheme 3) reacting with α-oxoketene dithioacetals with wide structural variation. However, when 1 carry the α-substituent the intermediate carbinol acetals 14 (Scheme 4) follow, different path to yield the corresponding indenes 15 in good yields. The cinnamoylketene dithioacetals 16 react with allyl anions to afford the corresponding methylthiostilbenes 18 (Scheme 5), while the homologous dithioacetal 20 failed to yield the corresponding 1,4-biaryl-1,3-diene 22 (Scheme 6). This limitation was circumvented by reacting 23 with allyl anions to afford the corresponding stilbenes 24, dienes 25 and triene 26 respectively. The...
TL;DR: In this article, two general versatile approaches to sulfur-containing pyrroles were proposed: (i) via sulfurcontaining ketones, particularly such as acylated aryl sulfides or thiophenes, and (ii) via thiylation reactions (including those via metallation) of N-vinylpyrrole or dithiocarbonization of pyrrole available from the reaction of ketoximes with acetylene or its synthetic equivalents.
Abstract: The ketoxime-acetylene-based pyrrole synthesis provides two general versatile approaches to sulfur-containing pyrroles: (i) via sulfur-containing ketones, particularly such as acylated aryl sulfides or thiophenes and (ii) via thiylation reactions (including those via metallation) of N-vinylpyrroles or dithiocarbonization of pyrroles available from the reaction of ketoximes with acetylene or its synthetic equivalents. Syntheses of alkylthiopyrroles, alkylthioarylpyrroles, 2-(2-thienyl)pyrroles (and their N-vinyl derivatives), N-(alkylthio or arylthio)ethylpyrroles, pyrrole-1 - and pyrrole-2-dithiocarboxylates (by the reaction of pyrroles with carbon disulfide) and their derivatives such as functionalized 2-(1-alkylthiovinyl)pyrroles, 1-alkylthio-3-imino-3H-pyrrolizines, 1-alkylthio-3H-pyrrolizin-3-ones, are discussed.
TL;DR: Tetraethyl ethenylidene bis phosphonate can undergo facile Michael type addition reaction with amines, alcohols, water, aminoacid and spirophosphoranes bearing a P[sbnd]H bond as discussed by the authors.
Abstract: Tetraethyl ethenylidene bis phosphonate can undergo facile Michael type addition reaction with amines, alcohols, water, aminoacid and spirophosphoranes bearing a P[sbnd]H bond. The stability of these compounds was investigated and the reversibility of the reaction was demonstrated in the case of methylamine.
TL;DR: Amino-phosphonic acids and their diethyl esters containing one or two pyridyl moieties were synthetized in good yields, starting from the corresponding Shiff base as precursors as discussed by the authors.
Abstract: Amino-phosphonic acids and their diethyl esters containing one or two pyridyl moieties were synthetized in good yields, starting from the corresponding Shiff base as precursors. The new compounds were characterized by 1H- and 31P-NMR spectroscopy and preliminary results indicate that they are able to complex with transition metals. Therefore, such compounds can be of utility in diagnostic medicine, NMR imaging and in agrochemistry.
TL;DR: S-triphenyl and trialkylgermyl esters of dialkyl dithio- and tetrathiophosphoric acids, and 4-methoxyphenyldithio and trithiophosphonic acids were easily obtained in the reactions of tetraphosphorus decasulfide as mentioned in this paper.
Abstract: S-Triphenyl and trialkylgermyl esters of dialkyl dithio- and tetrathiophosphoric acids, and 4-methoxyphenyldithio- and trithiophosphonic acids were easily obtained in the reactions of tetraphosphorus decasulfide and Lawesson's reagent with triphenyl and trialkyl(alkoxy)germanes and (alkylthio)germanes.
TL;DR: In this article, the combination of the isolobal six-electron units RP and Se has been used to construct homocycles from a diphosphenel or cyclophosphine2-4 and elemental selenium.
Abstract: Heterocycles (RP)n,Sem, formally derive from the combination of the isolobal six-electron units RP and Se. In this sense they can be prepared from a diphosphenel1 or a cyclophosphine2-4 and elemental selenium.
TL;DR: The Meyer reaction with 3-chloropropane-1,2-diol is first order in As(III) and first-order in glycidol as mentioned in this paper.
Abstract: The Meyer reaction of alkaline arsenious acid with glycidol is first order in As(III) and first order in glycidol. The kinetic and stereochemical evidence shows that the reaction follows an SN2 mechanism. The uncertainty in the pK 2 and, especially, pK 3 values for H3AsO3 does not distinguish between HAsO3 2- and AsO3 3- as the actual nucleophile in the Meyer reaction with glycidol as substrate. Kinetic runs and synthetic experiments point towards AsO3 3- as the most probable nucleophile. The Meyer reaction with 3-chloropropane-1,2-diol, proceeds either via glycidol or by direct displacement of chloride, in a ratio determined by the starting stoichiometry. HAsO3 2- does not react with the chlorodiol, thus leaving AsO3 3- as the nucleophile in the Meyer reaction.