Bristol-Myers Squibb (Germany)
Publishes on Asymmetric Hydrogenation and Catalysis, Asymmetric Synthesis and Catalysis, Chemical Synthesis and Analysis. 40 papers and 6.7k citations.
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Huisgen's 1,3-dipolar cycloadditions become nonconcerted when copper(I) acetylides react with azides and nitrile oxides, providing ready access to 1,4-disubstituted 1,2,3-triazoles and 3,4-disubstituted isoxazoles, respectively. The process is highly reliable and exhibits an unusually wide scope with respect to both components. Computational studies revealed a stepwise mechanism involving unprecedented metallacycle intermediates, which appear to be common for a variety of dipoles.
The copper-catalyzed cycloaddition reaction between azides and alkynes functions efficiently in aqueous solution in the presence of a tris(triazolyl)amine ligand. The process has been employed to make rapid and reliable covalent connections to micromolar concentrations of protein decorated with either of the reactive moieties. The chelating ligand plays a crucial role in stabilizing the Cu(I) oxidation state and protecting the protein from Cu(triazole)-induced denaturation. Because the azide and alkyne groups themselves are unreactive with protein residues or other biomolecules, their ligation is of potential utility as a general bioconjugation method.
Polytriazolylamines were synthesized by the copper(I)-catalyzed ligation of azides and alkynes. The C3-symmetric derivative, TBTA, was shown to be a powerful stabilizing ligand for copper(I), protecting it from oxidation and disproportionation, while enhancing its catalytic activity.
Abstract Enantioselective catalytic formation of tertiary stereogenic centers has nowadays reached an impressive level of maturity, as is reflected in the large variety of available methods that afford high yields and high stereoselectivities. However, the development of stereoselective approaches for the formation of quaternary stereogenic centers still represents an enormous challenge for synthetic chemists. On the other hand, biologically active molecules containing quaternary stereogenic centers provide an incentive for the development of new, selective, and useful processes. Over the last few years, breakthrough work relating to the formation of fully substituted carbon centers has appeared in the literature. In this review we discuss recent highlights of this new direction in catalysis research: the formation of quaternary stereogenic centers by enantioselective catalytic methodologies.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Abstract Acetylenes represent a class of versatile building blocks, which are widely used in organic synthesis. Over the past years, a considerable number of publications have appeared that focus on the enantioselective addition of acetylenes to carbonyls and imines. In addition, novel applications for acetylenes have emerged in the literature. We herein present an overview of recent results in these areas. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)