131 research outputs found
Diastereospecific Bis-alkoxycarbonylation of 1,2-Disubstituted Olefins Catalyzed by Aryl α-Diimine Palladium(II) Catalysts
Readily synthesized aryl α-diimine derivatives have been used as efficient ligands for the palladium-catalyzed oxidative bis-alkoxycarbonylation reaction of 1,2-disubstituted olefins. The most active catalyst A was formed in situ from bis-(2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabutadiene and Pd(TFA)2 (TFA=trifluoroacetate). This catalytic system was able to selectively convert 1,2-disubstituted olefins into 2,3-disubstituted-succinic diesters with total diastereospecificity, in good yields (up to 97%) with 2 mol% of catalyst loading, under mild reaction conditions (4 bar of CO at 20 °C in presence of p- toluenesulfonic acid as additive and p-benzoquinone as oxidant). The optimized reaction conditions could be successfully applied to 1,2-disubstituted aromatic, aliphatic, cyclic olefins and to unsaturated fatty acid methyl esters, employing methanol or benzyl alcohol as nucleophiles. The use of the bulky, less reactive isopropyl alcohol has allowed to better understand the mechanisms involved in the catalytic process. The geometry of the carbonylated products can be explained as a consequence of a concerted syn addition of the Pd-alkoxycarbonyl moiety to the olefin C=C bond. Catalyst A was isolated, characterized and analyzed by single crystal X-ray diffraction analysis. (Figure presented.)
Computationally guided discovery of a reactive, hydrophilic <i>trans</i> -5-oxocene dienophile for bioorthogonal labeling
ChemInform Abstract: Synthesis of Substituted Phenyl-, Biphenyl-, and Terphenylcarbaldehydes by Coupling of Arylpalladium Complexes with Alkyl- and Aryl-Grignard Reagents.
ChemInform Abstract: Arylation of Phenols. Convenient, Regiospecific Methods for Mono- or Bis-p-fluorophenylations, Suitable for Large Scale Syntheses.
ChemInform Abstract: Asymmetric Hydrogenation of 2-Benzylidenesuccinic Acid 4-((4-BOC-Amino) -1-piperidide) Monoamide: Key Step in a Process for Large Scale Preparation of a Renin Inhibitor.
ChemInform Abstract: Efficient Synthesis of (R)- and (S)-(6,6′-Difluorobiphenyl-2,2′-diyl) bis(diphenylphosphine); Electron-Poor Biphenyl-Type Ligands for Transition Metal Catalysts.
ChemInform Abstract: DEAMINATION OF N-(2,5-DIOXABICYCLO(4.1.0)HEPT-EXO-7-YL)-N-NITROSOUREA
ChemInform Abstract: Efficient, Simple Procedures for the Large-Scale Preparation of Building Blocks for Angiotensin II Receptor Antagonists.
ChemInform Abstract: Asymmetric C=C - Hydrogenation of a Substrate with Sulfur Functionality. Influence of Solvent and Substrate Configuration on Enantioselectivity.
ChemInform Abstract: DEAMINATION OF N-(2-OXABICYCLO(4.1.0)HEPT-7-EXO-YL)-N-NITROSOUREA. ATTEMPTED GENERATION OF A HETEROCYCLIC TRANS-CYCLOHEPTENE DERIVATIVE
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