Ratnasamy Somanathan

Asymmetric synthesis of amathamides A and B: novel alkaloids isolated from Amathia wilsoni

Abstract Syntheses of the amathamides A and B ((2S)-N-[(E and Z)-2(2,4-dibromo-5-methoxyphenylethenyl]-1-methyl-2-pyrrolinecarboxamides), new alkaloids isolated from the Tasmanian marine bryozoan Amathia wilsoni, were accomplished by a sequence of reactions starting from 3-hydroxybenzaldehyde.

Synthesis of homochiral pentadentate sulfonamide-based ligands

Abstract A two-step synthesis of pentadentate, tetraionic ligands based on sulfonamide, amide, and pyridyl groups is reported. These ligands are easily accessible in good to excellent yield from commercially available materials.

Asymmetric Transfer Hydrogenation of Prochiral Ketones in Aqueous Media with Chiral Water-Soluble and Heterogenized Bifunctional Catalysts of the RhCp*-Type Ligand

Asymmetric transfer hydrogenation (ATH) of prochiral aromatic ketones was carried out with a water-soluble complex of Rh(III)Cp* and mononitrobenzenesulfonamide bidentate ligand (1R,2R)-N-(2-aminocyclohexyl)-4-nitrobenzenesulfonamide 1 derived from chiral cyclohexane-1,2-diamine. Aqueous sodium formate was used as the hydride source. The reaction afforded the chiral alcohols in good enantioselectivities (79-93%) and yields (>99%). The modified monosulfonamide ligand was also covalently immobilized on solid phase such as silica, resin, and mesoporous SBA-15 silica and then explored as a catalyst with Rh(III)Cp* in the ATH of acetophenone.

Triphosgene/Triphenylphosphine: A Mild Reagent for the Conversion of Alcohols to Chlorides

Abstract A mixture of triphosgene/triphenylphosphine in methylene chloride converts primary and secondary alcohols to chlorides at room temperature.

Syntheses of Natural Hydroxyamides Using Trimethylsilyl Cyanide

Abstract New syntheses of tembamide (1), aegeline (2), and other hydroxyamides, using trimethylsilyl cyanide, are described.

Asymmetric transfer hydrogenation of ketones in aqueous solution catalyzed by rhodium(III) complexes with C2-symmetric fluorene-ligands containing chiral (1R,2R)-cyclohexane-1,2-diamine

Dois ligantes C2-simetricos bis(sulfonamide) contendo o fluoreno-quiral (1R,2R)-ciclohexano-1,2-diamina foram complexados com RhIII(Cp*) e usados como catalizador para reducao aromatica de cetonas. Os alcoois secundarios correspondentes foram obtidos com ee 87-100% e rendimento de 85-99%, sob condicoes de transferencia de hidrogenio assimetrica (THA), usando formato de sodio aquoso como fonte de hidretos. Usando acetofenona, obteve-se ee de 94% e rendimento de 86-97%, com uma razao substrato/catalizador de 10.000.

Synthesis of Tuberine

Abstract Tuberine, has been synthesized by syn sulfoxide elimination to introduce the enamide function.

Improved Syntheses of Peptide Coupling Reagents Bop and PyBOP Using Triphosgene

Abstract Synthesis of Benzotriazolyloxy tris [dimethyl-amino] phosphonium hexafluorophosphate (BOP) and Benzotriazolyloxy tris [pyrrolidino] phosphonium hexafluorophosphate (PyBOP), using triphosgene and hydroxybenzotriazole.

Synthesis of Chiral Aromatic Alcohols: Use of New C2-Symmetric RhIIICp∗, RuII(cymene), or RuII(benzene) Complexes Containing Chiral Diaminocyclohexane Ligand as Asymmetric Transfer Hydrogenation Catalyst

Abstract Twelve chiral secondary alcohols were synthesized by asymmetric transfer hydrogenation (ATH) using C2-symmetric bis(sulfonamide) ligand (2) derived from (1R,2R)-cyclohexane-1,2-diamine and complexed with [RhCl2Cp*]2, [RuCl2(cymene)]2, or [RuCl2(benzene)]2 and then used in situ in the reduction of prochiral ketones. The alcohols were obtained in 85–99% yield and 90–99% enantioselectivity with isopropanol as the hydrogen source. Two-fold rate enhancement and better yields were achieved (88–99%) with 80–99% enantioselectivity using the complex [RhCl2Cp*]2 and aqueous sodium formate as the hydrogen source.

CONVENIENT SYNTHESIS OF 1-OXA-3,8-DIAZASPIRO 4,5 DECAN-2-ONES

Abstract Synthesis of 1-oxa-3,8-diazospiro [4,5] decan-2-ones from 4-pyridone by addition of trimethylsilyl cyanide.