Showing papers in "Phosphorus Sulfur and Silicon and The Related Elements in 1999"
TL;DR: In this article, a 64 X 64 Mercury-Cadmium-Telluride (MCT) focalplane array detector attached to a Fourier transform infrared (FT-IR) microscope was used to spectroscopically image 5-μm sections of human bone tissue in the fingerprint region of the infrared spectrum.
Abstract: A 64 X 64 Mercury-Cadmium-Telluride (MCT) focal-plane array detector attached to a Fourier transform infrared (FT-IR) microscope was used to spectroscopically image 5-μm sections of human bone tissue in the fingerprint region of the infrared spectrum. Infrared band contours in the 1200–900 cm−1 spectral region, due to phosphorous-containing mineral, change shape as a function of radial distance from centers of bone growth, called osteons. This technique is providing new insights into the biomineralization process.
84 citations
TL;DR: Agarwal et al. as discussed by the authors found that red phosphorus and ammonium polyphosphate interact with nylon 6 under burning conditions to produce phosphate esters and eventually chars, and tried to find synergists for phosphorus provide clues to improved combinations.
Abstract: Phosphorus-based flame retardants have diverse modes of action, Aryl phosphates can have vapor phase action in styrenic polymers but also can contribute to producing a barrier layer. Tris(dichloroisopropyl) phosphate in a flexible polyurethane foam can serve as both a vapor-phase (probably physical) flame inhibitor in bottom ignition but contributes to formation of a barrier in top-down burning. Halogen/phosphorus and nitrogen/phosphorus synergism are not general but examples are known. Red phosphorus and ammonium polyphosphate interact with nylon 6 under burning conditions to produce phosphate esters and eventually chars. The cyclic neopentyl ester of nitrilotris(methylphosphonic acid) as a flame retardant in ethylene vinyl acetate copolymer can serve as a char-former and catalyst. Attempts to find synergists for phosphorus provide clues to improved combinations.
50 citations
TL;DR: In this paper, S-Propargyl xanthates exihibit a special behavior which involves a sigmatropic rearrangement to the corresponding allene and ring closure to a novel betaine.
Abstract: Xanthates are convenient precursors of a variety of radicals that can be captured in an inter-or intramolecular fashion. Overall, the process involves rupture of the sulfide C-S bond and addition of the elements of the xanthate to the olefinic trap. The xanthate in the product can be used in another radical sequence or ionically modified in a grear variety of ways. S-Propargyl xanthates exihibit a special but interesting behaviour which involves a sigmatropic rearrangement to the corresponding allene and ring closure to a novel betaine.
42 citations
TL;DR: These studies have increased the understanding of the optimal spatial arrangement of the nitrogen and phosphonate moieties required to give the bisphosphonate molecules the geometry necessary for potent antiresorptive activity on bone.
Abstract: Risedronate was selected for clinical development from a library of more than 200 bisphosphonate analogs for the treatment of a variety of bone diseases. It is a pyridinyl bisphosphonate and is therefore characterized by a nitrogen residue in its structure. Our studies have increased the understanding of the optimal spatial arrangement of the nitrogen and phosphonate moieties required to give the bisphosphonate molecules the geometry necessary for potent antiresorptive activity on bone. A series of aminophenylethane phosphonates have been studied to further demonstrate these geometric requirements.
36 citations
TL;DR: In this paper, the antimicrobial activity of the newly synthesized compounds was tested based on elemental analyses and spectral data, and several cycloaddition reactions were carried out on 3, 5, 6, and 6a-c with dienophiles 7a,b, and 8a,c, respectively.
Abstract: Dibenzalacetones 1a-c reacted with cyanothioacetamide (2) to give the new styrylpyridinethione derivatives 3a-c which were used as the starting materials for the synthesis of other several heterocyclic compounds. Reactions with chloroacetone (4). N-arylmaleimides 7a,b, and ethyl iodide gave 2-S-acetonyl pyridines 5a-c, pyrrolo[3,4-flquinolines 9a-f, and 2-S-ethylpyridines lla-c, respectively. Several cycloaddition reactions were carried out on 3a-c, 5a-c, and 6a-c with dienophiles 7a,b, to afford the corresponding cycloadducts 9a-f, 10a-f, and 8a-f, respectively. Structures were established based on elemental analyses and spectral data. The antimicrobial activity of the newly synthesized compounds was tested.
33 citations
TL;DR: Several bis-thiazolidinone derivatives 6a-e, 9a,b and 13a-b have been synthesized and have discussed the IR, 1H-NMR, 13C-nMR and mass spectra of these compounds as mentioned in this paper.
Abstract: Several bis-thiazolidinone derivatives 6a-e, 9a,b and 13a,b have been synthesized and have discussed the IR, 1H-NMR, 13C-NMR and mass spectra of these compounds. Compounds 6a-e have also been screened in vitro for antibacterial activities.
32 citations
TL;DR: The reaction of thiocyanoacetamide with α,β-unsaturated ketones2a,b resulted in the formation of the corresponding newly synthesized 1(H)-pyridinethione derivatives3a, b, which were used as synthons for the preparation of 2-S-alkyl-, 2-s-aryl, 2- S-acetamidopyridine, thieno[2,3-b]pyridine and pyraz
Abstract: The reaction of thiocyanoacetamide (1) with α,β-unsatumted ketones 2a,b resulted in the formation of the corresponding newly synthesized 1(H)pyridinethione derivatives 3a,b. Compounds 3a,b were used as synthons for the preparation of 2-S-alkyl-, 2-S-aryl-, 2-S-acetamidopyridine, thieno[2,3-b]pyridine and pyrazolo[3,4-b]pyridine derivatives via a wide range of reactions with different reagents. The antimicrobial activity of some of the newly synthesized compounds was tested. Compounds 3a, 11a, 15a, and 19a,b were found to be the most active ones.
28 citations
TL;DR: In this paper, the addition of thiocyante ion to epoxides to afford s-hydroxy thiocyanates in high yields and regioselectivity is described.
Abstract: 2,3-Dichloro-5,6-dicyanobenzoquinone (DDQ) catalyses the addition of thiocyante ion to epoxides to afford s-hydroxy thiocyanates in high yields and regioselectivity.
27 citations
TL;DR: In this article, the enantiopure diphosphine was fully characterized by X-ray diffractometric analysis and was resolved in an enantiomerically pure state through a kinetic resolution process effected by complexation of the racemate with half of a chiral aminopalladium complex.
Abstract: 2,2'-Bis(diphenylphosphino)-1,1'-bibenzimidazole BIMIP) was resolved in an enantiomerically pure state through a kinetic resolution process effected by complexation of the racemate with half of the stoichiometric amount of a chiral aminopalladium complex. The enantiopure diphosphine was fully characterized by X-ray diffractometric analysis.
27 citations
TL;DR: In this article, the synthesis of alkyl hydrogen isopropyl phosphonic dichloride reacts in a unique fashion to produce alkyly hydrogen isophropylphosphonates in moderate yields.
Abstract: The synthesis of alkyl hydrogen alkylphosphonates 1 was studied. Different synthetic routes were investigated and it was found that alkylphosphonic anhydrides can serve as ideal precursors for the synthesis of those half-acids. It was also shown that isopropyl phosphonic dichloride reacts in a unique fashion to produce alkyl hydrogen isopropylphosphonates in moderate yields.
27 citations
TL;DR: In this article, a tricyclic cycloadducts with a 2,2'-connection of pyrrolidine and phospholane rings and five to seven contiguous stereogenic centers have been induced and one or two resolved during the cycloaddition process.
Abstract: Enantiopure five-membered ring nitrones derived from L-tartaric acid and from L-malic acid undergo highly regio- and stereoselective cycloaddition reactions with an excess of racemic 2,3-dihydro-l-phenyl-1H-phospholes producing two readily separable tricyclic cycloadducts and concomitantly effecting kinetic resolution of the dihydrophosphole derivative. Stereochemistry of the cycloaddition process and scope of the kinetic resolution process have been established in details and adjusted to produce dihydrophosphole derivatives in good yields and in very high optical purity. To effect syntheses of single cycloadducts of 100% ee the techniques of doubly asymmetric synthesis and parallel kinetic resolutions have been employed. The resulting tricyclic cycloadducts feature 2,2'-connection of pyrrolidine and phospholane rings and five to seven contiguous stereogenic centers of which three have been induced and one or two kinetically resolved during the cycloaddition process.
TL;DR: In this paper, the Homer-Wittig reaction between formaldehyde and methylene diphosphonate is described for 2-phosphorylated 3-halopropenes.
Abstract: Under suitable reaction conditions 2-phosphorylated 3-chloropropene 1 monoalkylates methoxide, ethoxide, thiocyanate, methyl and ally1 Grignard reagents and acetamidomalonate—the latter reactions leading to 2-phosphorylated 1-butene, 1,5-hexadiene and C-alkylated α-aminoacids. Diethyl malonate and ethyl acetoacetate give mixtures of mono and dialkylated products whereas ethyl cyanoacetate gives only dialkylated product. Acetylacetone gives a dialkylated product - the monoalkylated intermediate undergoing acyl cleavage to give 2-phosphorylated 5-hexene-2-one as the major product. A new simple route for the preparation of 2-phosphorylated 3-halopropenes via a Homer-Wittig reaction between formaldehyde and methylene diphosphonate is described.
TL;DR: Conjugates prepared by immobilizing thiol-terminated oligonucleotides onto gold nanoparticles form stable colloidal solutions in aqueous media that can serve as linkers to organize the gold particles reversibly into three dimensional assemblies.
Abstract: Conjugates prepared by immobilizing thiol-terminated oligonucleotides onto gold nanoparticles form stable colloidal solutions in aqueous media. The oligonucleotides can serve as linkers to organize the gold particles reversibly into three dimensional assemblies, and the gold particles can function as colorimetric reporters for hybridization of the bound oligomers with target oligonucleotides in solution.
TL;DR: In this article, it was shown that stencal hindered compounds 2a-f up to 315°C leads to the corresponding bicyclic phosphites 3a-d while the non-hindered phosphocins 2g-i react in refluxing xylene to give phosphite 3e-g.
Abstract: Hexaalkylphosphorous triamides form in good yields 6-dialkylamino-12H-dibenzo[d.g] [1,3,2]dioxaphosphocins 2a-i in the reaction with oligophenols 1a-i. Heating the stencal hindered compounds 2a-f up to 315°C leads to the corresponding bicyclic phosphites 3a-d while the non-hindered phosphocins 2g-i react in refluxing xylene to give phosphites 3e-g. The phosphocin 2i formed another phosphocin 2i* during heating to 90°C in THF by “wandering” of the phosphorus moiety. The bicyclic phosphites 3h and 3i were prepared starting from tetraphenol 1h and pentaphenol 1i by reaction with hexaethylphosphorous triamide in refluxing xylene. The diphosphorylated triphenol 4 and tetraphenol 5 are formed in the reaction of the corresponding phenols with 2 eq. of hexaalkylphosphorous triamide.
TL;DR: In this paper, the interaction of cyanothioformamides with chalcones gave 3-amino-2-mercaptopyrroles, which have the tautomeric structures (3-aminopyrronline-2 -thiones and 3-iminopyrrolidine-2 thiones) and the latter was reacted with chloroacetic acid, ethyl chloroacetate, chlorocoracetate and 2,3-dichloro-l,4-naphthoquinone to give
Abstract: Interaction of cyanothioformamides with chalcones gave 3-amino-2-mercaptopyrroles, which have the tautomeric structures (3-aminopyrroline-2-thiones and 3-iminopyrrolidine-2-thiones). The latter was reacted with chloroacetic acid, ethyl chloroacetate, chloroacetamide and 2,3-dichloro-l,4-naphthoquinone to give the corresponding pyrrolothiazines derivatives. On using phenylisocyanate or p-chlorobenzoyl chloride, the corresponding pyrrolothiazole derivatives could be isolated. Replacement of chalcones by maleimides furnished pyrrolopyrrolinediones.
TL;DR: Investigations demonstrated that there are distinct bioisosteric relationships between the C/Si/Ge analogues studied, including centrochiral enantiomerically pure germanes using biotransformations with whole microorganisms or isolated enzymes.
Abstract: In context with systematic investigations on C/Si/Ge bioisosterism, the following studies were carried out: (a) synthesis and pharmacological characterization of centrochiral enantiomerically pure germanium-based muscarinic antagonists; (b) synthesis and pharmacological characterization of a germanium-containing decapeptide; (c) studies on the metabolism of a germanium-based drug in the rat; (d) synthesis of centrochiral enantiomerically pure germanes using biotransformations with whole microorganisms or isolated enzymes. These investigations demonstrated that there are distinct bioisosteric relationships between the C/Si/Ge analogues studied.
TL;DR: The reactivity of thiophene derivatives towards active methylene reagents, aryledenernalononitriles were studied to afford several new thieno[2,3-b]pyridine derivatives as discussed by the authors.
Abstract: The reactivity of thiophene derivatives 1,2 and 3 towards active methylene reagents, aryledenernalononitriles were studied to afford several new thieno[2,3-b]pyridine derivatives. The biological activities of the synthesized products showed interesting results.
TL;DR: In this article, a simple route starting from N,N-disubstituted selenoureas has been elaborated and used for the synthesis of a series of highly reactive selenazoles.
Abstract: As a result of checking suited methods for preparing N,N-disubstituted 2-amino-selenazoles 14 as a nearly unknown class of highly reactive selenazoles a simple route starting from N,N-disubstituted selenoureas 12 has been elaborated and used for the synthesis of a series of these compounds. The necessary selenium-containing starting compounds 12 are available from N,N-disubstituted cyanamides 18 and hydrogen selenide.
TL;DR: In this article, a catalytic enantioselective oxidation of a range of sulfides is achieved by treatment with hydrogen peroxide in conjunction with enantiomerically pure sulfonylimines under basic conditions.
Abstract: Catalytic enantioselective oxidation of a range of sulfides is achieved in very high yields by treatment with hydrogen peroxide in conjunction with enantiomerically pure sulfonylimines under basic conditions. Enantioselectivities of up to ca. 98% or better were obtained using acetals of oxocamphorsulfonylimine as mediators. This process is clean, inexpensive and simple, requires minimum work up and no close monitoring. The reactive intermediate is currently formulated as an α-hydroperoxyamine.
TL;DR: In this article, the synthesis of castanospermine stereoisomers from ω-amino-γ-oxygenated-α and β-unsaturated sulfones with methylene active ketones is described.
Abstract: Herein we present some new synthetic applications based on the use of functionalized α,β-unsaturated sulfones and α,β-unsaturated sulfoxides. In particular, we have developed a stereodivergent approach to the synthesis of castanospermine stereoisomers from ω-amino-γ-oxygenated-α.β-unsaturated sulfones as well as a stereoselective synthesis of substituted dihydrofurans by Pd(0) catalyzed reaction of the carbonate derivatives of γ-oxygenated-α.β-unsaturated sulfones with methylene active ketones. Additionally, the use of the sulfinyl group as a novel chiral auxiliary in asymmetric Heck reactions is also described.
TL;DR: In this article, the imidazolidines (II) were reacted with amines, H2S and o-phenyhediamines to give 4-substituted imino derivatives (VI), thiohydantoin (VII) and 1-phenyl-3 -substitized-1H-imidazo[4,5-b]-quinoxaline-2-(3H)-ones(XIII), respectively.
Abstract: The imidazolidines (II) were reacted with amines, H2S and o-phenyhediamines to give 4-substituted imino derivatives (VI), thiohydantoin (VII) and 1-phenyl-3 -substituted-1H-imidazo[4,5-b]-quinoxaline-2-(3H)-ones(XIII), respectively. Interaction of the oxazolidines (V) with amines, o-phenylenediamines and o-aminophenol caused fission of the oxazole ring to produce (XIV, XVII & XIX) respectively.
TL;DR: In this paper, the authors focused on phosphorus compounds which can form complexes with the Ca2+ ions of hydroxyapatite, which can achieve a strong and durable bond to dentine.
Abstract: Introduction Achieving a strong and durable bond to dentine is of great importance in restorative techniques In recent years there has been a lot of debate as to how such a bond may be obtained Bonding is believed to occur through either mechanical or chemical interaction or possibly a combination of both[1] In this study we have focused on phosphorus compounds[2−4] which can form complexes with the Ca2+ ions of hydroxyapatite Most of the hitherto known compounds can not afford a single step procedure in dental adhesion To overcome this problem several new phosphonic and phosphoric methacrylates have been synthesized Furthermore, polymerization capabilities and characteristics of physical and adhesive properties are described
TL;DR: In this article, the molecular structures and syntheses of two types of organotin oxo-clusters, (RSn)12O14(OH)6}2+(X−)2 (Tin-12) and {RSnO(O2CR′)6 (TIN-6) are presented.
Abstract: The combination at the nanosize level of inorganic and organic components in a single material makes accessible an immense new area of materials science. Among other soft chemistry processes, sol-gel chemistry offers a versatile access to chemically designed new hybrid organic-inorganic materials. Yet, it might be inappropriate to prepare “model” hybrid materials, in which the structure of the organic and inorganic domains, together with those of their interface, are perfectly defined. Such systems, required to understand, optimize, and control the structure-properties relationship, can be alternatively prepared by assembling well-defined preformed inorganic nanobuilding blocks. The molecular structures and syntheses of two types of organotin oxo-clusters, {(RSn)12O14(OH)6}2+(X−)2 (“Tin-12”) and {RSnO(O2CR′)}6 (“Tin-6”) are presented. Various strategies to assemble them are discussed to illustrate the versatility of such nanobuilding blocks in the synthesis of hybrid systems with iono-covalent or ionic or...
TL;DR: In this article, the addition of compounds with a P-H bond to Schiff bases of both simple and macrocyclic compounds proceeds smoothly as a non-catalysed thermally initialised reaction in an inert solvent.
Abstract: Addition of compounds with a P-H bond to Schiff bases of both simple and macrocyclic compounds proceeds smoothly as a non catalysed thermally initialised reaction in an inert solvent. For macrocyclic systems and bulky phosphorus substituents a stereoselective formation of the trans isomer was confirmed by X ray analysis. The addition is reversible, and the reverse reaction is catalysed by Lewis acids. The trans orientation of phosphorus substituents on the macrocycle ring, the stereochemical rigidity of molecules and reversibility of the addition limit the use of the compounds formed in such manner as ligands.
TL;DR: In this paper, new specific routes to 1,2-diphosphete-, 1, 2-4-triphosphol-, and 1 2, 4 triphospholylπ-π-complexes are reported.
Abstract: New specific routes to 1,2-diphosphete-, 1,2,4-triphosphol-, and 1,2,4-triphospholyl-π-complexes are reported, which are based on dichloro-1,2-diphosphetene and 1-stannyl-1,2,4-triphosphol as the heterocyclic educts. Details are given for Sn, Mn, Fe, and Co complexes. ESR-data of paramagnetic 1,2,4-triphospholyl sandwich complexes of Co and Mn proof the absence of degenerate SOMOs in these cases.
TL;DR: In this paper, the Atherton-Tod method using potassium carbonate as a base in the presence of tetrabutylammonium bromide as a phase transfer catalyst or by the intermolecular condensation of the hydrazines 1 with phosphorochloridate, (R3O)(R4O)P(O)Cl, in presence of a base, triethylamine.
Abstract: β-(1,3-Benzothiazole-2-)phosphoric hydrazides 2 were synthesized by Atherton-Tod method using potassium carbonate as a base in the presence of tetrabutylammonium bromide as a phase transfer catalyst or by the intermolecular condensation of the hydrazines 1 with phosphorochloridate, (R3O)(R4O)P(O)Cl, in the presence of a base, triethylamine. Thermal decomposition at 180°C of 2a caused the intramolecular shift of ethyl group from oxygen to β -nitrogen atom, and formed the monoester phosphoric hdrazide 3, whose structure was determined by elementary analysis, IR, 1H NMR, 13C NMR, 31P NMR, MS spectra. The biological activity of the title product was also tested and some of them showed good fungicidal activity.
TL;DR: The feasibility of synthesizing α-hydroxy α-alkyl/aryl methyl-enebisphos-phonates via Grignard addition to tetraalkyl carbonylbisphosphonates 6 is demonstrated, and a new synthesis of 6 under very mild conditions is described.
Abstract: Some current and potential therapeutic uses of bisphosphonates and phosphonocarboxylates are summarized. The feasibility of synthesizing α-hydroxy α-alkyl/aryl methyl-enebisphos-phonates via Grignard addition to tetraalkyl carbonylbisphosphonates 6 is demonstrated, and a new synthesis of 6 under very mild conditions is described.
TL;DR: In this article, the optical integrity of sulfines having a stereogenic center at C-α is described and the Diels-Alder type cycloaddition reaction to give dihydrothiopyran S-oxides, with special focus on the asymmetric induction, is reported.
Abstract: Sulfines (thione S-oxides) are nonlinear sulfur centered heterocumulenes formally derived from sulfur dioxide by replacing one oxygen by a carbon atom. In the introduction historical highlights are presented. A section is devoted to some recent developments regarding the synthesis of sulfines, viz. via oxidation by dimethyl dioxirane, and the reaction of silyl enol ethers and active methylene compounds, respectively, with thionyl chloride in the presence of a tertiairy amine base. Enethiolization of sulfines to vinylsulfenic acid is discussed in terms of its entrapment by an intramolecular reaction with an olefin. In this context also the optical integrity of sulfines having a stereogenic center at C-α is described. In the final section the Diels-Alder type cycloaddition reaction to give dihydrothiopyran S-oxides, with special focus on the asymmetric induction, is reported.
TL;DR: In this article, a 2-benzothiazolyl-β-arylaminoacrylonitrile (III) was obtained by refluxing equimolar amounts of I11 and hydrazine, hydroxylamine, guandine ethylenediamine and ethanolamine in presence of DMF yielded the corresponding 2-pyra-2010, isoxazolo, pyrimidino, 1,4-diazepino and 1.4-oxazepinobenzothiazole (V-IX) respectively.
Abstract: Substituted benzothiazole at position 2 by a heterocyclic ring has been prepared by the action of bifunctional compounds on the active intermediate a-2-benzoth: azolyl-β-arylaminoacrylonitrile (III). Compound III was obtained by refluxing a-2-benzothiazolyl-β, β-dimethylthioacrylonitrile (II) with aromatic amines in ethanol for a long time. Refluxing equimolar amounts of I11 and hydrazine, hydroxylamine, guandine ethylenediamine and ethanolamine in presence of DMF yielded the corresponding 2-pyra- 2010, isoxazolo, pyrimidino, 1,4-diazepino and 1,4-oxazepinobenzothiazole (V-IX), respectively. The structures of all newly prepared compounds have been confirmed by analytical and spectral data.
TL;DR: The mechanism of their intramolecular synergism was investigated in this article, where the best overall stabilizers are 2,4-bis(alkylthiomethyl)-6-methylphenols.
Abstract: Alkyl-hydroxybenzylthioethers are efficient storage and processing stabilizers for elastomers and adhesives. Especially alkyl-(2-hydroxybenzyl)thioethers represent an intramolecular combination of a primary and secondary antioxidant, i.e. a phenolic and a thioether moiety in an optimized spatial arrangement. The mechanism of their intramolecular synergism was investigated. The best overall stabilizers are 2,4-bis(alkylthiomethyl)-6-methylphenols, e.g. AOl, in contrast to 2,6-dialkyl-4-alkylthiomethylphenols(B), 4-alkyl-2,6-bis(alkylthiomethyl)phenols C.