Efficient Chemoselective Mild Deprotection of S,Sand S,O-Acetals and Ketals with Electrophilic Halogens

A novel and simple method for the chemoselective deprotection of S,S- and S,O-acetals and ketals in the presence of their O,O-analogs with electrophilic halogens to their corresponding carbonyl compounds is described using N-bromosuccinimide, N-chlorosuccinimide, 2,4,4,6-tetrabromo-2,5-cyclohexen-1-one, trichlorocyanuric acid, or molecular bromine in aqueous acetonitrile. The use of these reagents in the presence of hydrated silica gel provide efficient, novel, and mild procedures for the deprotection of cyclic and acyclic O,O-, S,S-, and S,O-acetals and ketals in excellent yields in short reaction times.     

The Synthesis of Mono- and Bi-Metallic Platinum(II) and/or (IV) Complexes Containing the Ligand Bis(diphenylphosphino) Methylamine

Complexes of the type [Pt R₂ (dppma-PP′)] (R─Me, Et, Ph, CH₂Ph, C₆H₄ Me-p, C₆H₄OMe-2, CH₂CMe₃, 1-naphthyl, C₆H₄Me-o, dppma = Ph₂PNMe PPh₂) have been prepared from [PtCl₂, (dppma-PP′)] and the corresponding alkyl-lithium or Grignard reagents. Equilibrium constants, k, for the conversion of [PtR₂ (dppma-PP′)] into cis-[PtR₂(dppma-P)₂] with dppma were studied using ³¹P NMR spectroscopy at room temperature. Equilibrium is rapidly established for R─C₆H₄-Me-o, at 20°C. Complex of the type cis-[PtR₂ (dppma-P)₂] was isolated R─C₆H₄ Me-o. The complexes [PtMe₂(dppma-P)₂] and [Pt(o-methoxyphenyl)₂(dppma-P)₂] were prepared, but unfortunately decomposed once isolated, the only evidence for its formation being from ³¹P-{¹H} NMZR spectroscopy. The o-tolyl or 1-naphthyl complexes exist as syn-anti mixtures in solution, due to restricted rotation around the platinum aryl bonds. Treatment of several complexes of the type [PtR₂(dppma-PP′)] with MeI gives [PtR₂Me(I)(dppma-PP′)] with trans addition of MeI. Treatment of [PtR₂(dppma-PP′)] with HCl gives [Pt Cl (R) (dppma-PP′)] for R─C₆H₂Me₃-2,4,6, C₆H₄-CH₃-2, C₆H₄-Me-4, Me, 1-naphthyl. The ¹H, ³¹P NMR parameters for these complexes are discussed. Attempted preparation of complexes of the type [PtR₂ (dppma-P)₂M] (R─C₆H₄-Me-2, Me CN-C₆H₄-Me-4); M─Pd, Pt, Au,) are reported.     

Synthesis and Antibacterial Activity of Some New S-Triazole Derivatives

Abstract

Alkylation of 4-anilino-5-phenyl-4H-1,2,4-triazole-3-thiol (1) with some halo compounds yielded the corresponding sulfides 2a–f. Some sulfides 2e,f were cyclized to give triazolothiadiazines 3 and 4. Triazolothiadiazoles 5 and 6 were prepared through the reaction of compound 1 with carbon disulfide or ethyl orthoformate, respectively. Treatment of compound 1 with ethyl chloroformate or phenyl isothiocyanate yielded triazolo-thiadiazole and triazole 9 and 10, respectively. Reaction of compound 1 with Lawesson's reagent gave triazolothiadiazaphosphole derivative 11. Also, compound 1 underwent cyclocondensation reactions with some bidentate reagents to give triazolothiazines 4, 12, and 13. Triazolo-thiazepines and triaziepine 14–16 were synthesized via the reaction of compound 1 with β-ketoesters or ethyl cyanoacetate. Tricyclic systems 19 and 20 were prepared through the reaction of compound 4 with the appropriate reagent. Some synthesized compounds were tested for antibacterial activity.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

KF/Al2O3 as an Efficient,Green, and Reusable Catalytic System for the Solvent-Free Synthesis of N-Alkyl Derivatives of Sulfonamides via Michael Reactions

KF/Al ₂ O ₃ efficiently catalyzes the microwave-assisted Michael addition of sulfonamides to α,β-unsaturated esters under solvent-free conditions to afford N-alkyl derivatives of sulfonamides as biologically interesting compounds in high yields and in short reaction times. In this reaction, N,N-dialkylsulfonamides are also produced, but in very low yields.     

Dithiocarbamates as Precursors in Organic Chemistry; Synthesis and Uses

Abstract

Organic dithiocarbamates have received great attention due to their interesting chemistry and wide utility as radical precursors and intermediates in organic synthesis. They also have found many of applications, that is, in agriculture and medicine. They are in use as pesticides, as well as in the rubber industries as vulcanization accelerators; and as antioxidants. Because they exhibit strong metal-binding capacity, they can act as in inhibitors of enzymes and have a profound effect on biological systems. Moreover, they have found application in the treatment of cancer and HIV.     

SOME REACTIONS OF 3-AMINO-2-CARBOETHOXY-4,6-DIMETHYLTHIENO[2,3-b]-PYRIDINE. SYNTHESIS OF SOME NEW THIENOPYRIDOPYRIMIDINES

Abstract

Thienopyridine oxazinone (1) has been prepared and explored as a precursor by its reaction with some reagents namely, ammonium acetate, aliphatic amines, aromatic amines, hydrazine hydrate, thiosemicarbazide, and ethyl glycinate to give pyridothienopyrimidines (11-VII). The pyrimidinone compound (11) was converted to the 4-chloro derivative (X) by its reaction with excess POCl₃ Interaction of the 4-chlorocompound (X) with some reagents namely, hydrazine hydrate, methyl amine, aniline, sodium thiophenolate, ethyl glycinate, thiosemicarbazide and thiourea, yielded pyridothieno-pyrimidine derivatives (XI-XVII) substituted at 4-position, respectively.     

SYNTHESIS AND BIOLOGICAL ACTIVITY OF SOME NEW 8-HYDROXYQUINOLINE SULPHONAMIDE DERIVATIVES

Abstract

Some new derivatives containing both 8-hydroxyquinoline and sulphonylamino β-lactams and thiazolidinones have been prepared. These compounds were synthesized from the corresponding 8-hydroxyquinoline sulphonylhydrazide (1) by converting it to hydrazones (2). The latter hydrazones (2) were easily transformed to β-lactams (3) and thiazolidinones (4) by cyclocondensation reaction with chloroacetyl chloride and/or mercaptoacetic acid. Some metal chelates with Fe³⁺. Co²⁺+, Ni²⁺, Cu²⁺ and Cd²⁺ have been prepared for some of the compounds and screened in vitro for their biological activity.     

Synthesis of Novel Semiconducting Aromatic Polyesteramids Containing Pyridine: Characterization of Nanometer-Sized Rod-Like Analogues and their Copper (II) Complexes

In this paper, new thermally stable isomeric unsubstituted polyesteramides have been successfully prepared by condensation of aromatic acids chlorides namely; isophthaloyl, pyridine-3,5-dicarbonyl and pyridine-2,6-pyridine-dicarbonyl dichlorides with the aminophenol isomers in NMP. Conducting the reaction in NMP/H₂O (90/10 v/v) followed by centrifugal separation furnished the desired polymers as rod-like nanoparticles. The morphology of obtained nanoparticles were studied by SEM. Mixing NMP with H₂O was essential for controlling the particles morphology and as a reaction accelerator.

Pyridine-containing polymers exhibit semi-conducting nature as their conductivities increase with increasing temperature, while no variation of the conductivity with the temperature was observed for their corresponding phenylene analogues. Introduction of the nitro group into the polymer backbone led to a red shift in the absorption and the obtained polymers have a bright yellow color, which is unusual with this polymer group. Copper (II) ions were complexed the polyesteramides-containing nitro group in a (1:1) ratio. Complexes of pyridine-containing polymers exhibit semiconducting nature changed to metallic characters on heating and their conductivities increased tens of magnitudes than their corresponding ligands. These new types of polymeric materials and their nano-sized rods may have numerous applications in nanotechnology and their properties can be tuned for specific applications such as conducting adhesives and coating materials.     

Magnetic Polymer Composite Particles Via In situ Inverse Miniemulsion Polymerization Process

We aimed at preparing magnetic iron oxide particles by the oxidation-precipitation method in order to encapsulate these particles in polymer matrices composed of poly(acrylamide-styrene sulfonic acid sodium salt). Nanocomposites were synthesized by the incorporation of surface treated magnetic nanoparticles in the synthesized polymers via in situ inverse mini-emulsion polymerization process. The study parameter was the ionic monomer content in the synthesized polymers. The structure and the morphology of the magnetic nanogels were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). FTIR and XRD showed that pure magnetite was formed and successfully encapsulated in the composite nanoparticles. The polymer encapsulation could reduce the susceptibility to leaching and could protect the magnetite particle surfaces from oxidation. The ionic monomer content had a great effect on the magnetization behavior. Magnetite prepared by the oxidation precipitation method, of 50 nm mean particle size, was embedded successfully into the polymer nanogels with a reasonable magnetic response, as proved by vibrating sample magnetometer measurement. Magnetic nanocomposites were proven to be super-ferromagnetic materials.     

New Coordination Polymers of 1,4-Bis(2″-Hydroxyphenylazomethine) Phenylene

Coordination polymers of 1,4-bis(2′-hydroxyphenylazomethine) phenylene have been prepared with the metal ions Ti(III), Cr(III), Fe(III), Mn(II), Ni(II), and Cu(II). They were characterized by elemental analysis, IR, and electronic spectra. The metal contents in all polymers were found to be consistent with a 1:1 (metal:ligand) stoichiometry. The thermal behavior of these coordination polymers has been studied by thermogravimetric analysis in air up to 750°C, and the data showed that they are thermally stable up to 200°C. Physical properties such as the solubility and viscosity of the polymer complexes were also determined. Electrical conductivity measurements of the synthesized polychelated polymers showed that they are insulators except for the Ni(II) complex which shows a semiconducting character. Mössbauer data clearly establish the 3 + oxidation state for the iron complex polymer.