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Lyndon C. Xavier

Bio: Lyndon C. Xavier is an academic researcher from Merck & Co.. The author has contributed to research in topics: Aryl & Enantioselective synthesis. The author has an hindex of 10, co-authored 21 publications receiving 570 citations.

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TL;DR: An extraordinarily mild procedure for the synthesis of 2-aryl and 2-alkenyl-substituted carbapenems via palladium-catalyzed coupling of a vinyl triflate with aryl or vinyl boronic acids is described in this article.

36 citations

Journal ArticleDOI
TL;DR: This approach offers a general method for the preparation of the 3-aryl carbapenems, which possess strong antibacterial activity against resistant strains.
Abstract: Anti-MRSA carbapenem, L-742,728, has been prepared in large quantity using the Suzuki−Miyaura cross-coupling as the key reaction. Three approaches have been examined by varying the coupling reaction between carbapenem nucleus A and side chains B, BC, and BCD, wherein BCD represents the fully elaborated side chain. The coupling of A with BCD offers the advantage of convergence and requires fewer chemical steps after installation of the thermally unstable carbapenem skeleton. This key reaction highlights the versatility and efficiency of the Suzuki−Miyaura reaction. This approach offers a general method for the preparation of the 3-aryl carbapenems, which possess strong antibacterial activity against resistant strains.

29 citations

Journal ArticleDOI
TL;DR: In this paper, anilines were acylated by nitriles in the presence of BCl 3 and a second Lewis acid and yield improvements were obtained based on recognition that the chloride affinity of the second acid governs supercomplex formation.

21 citations


Cited by
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TL;DR: The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center.
Abstract: Hydrogenation is a core technology in chemical synthesis. High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center. This catalyst system allows for the preferential reduction of a C=O function over a coexisting C=C linkage in a 2-propanol solution containing an alkaline base. The hydrogenation tolerates many substituents including F, Cl, Br, I, CF(3), OCH(3), OCH(2)C(6)H(5), COOCH(CH(3))(2), NO(2), NH(2), and NRCOR as well as various electron-rich and -deficient heterocycles. Furthermore, stereoselectivity is easily controlled by the electronic and steric properties (bulkiness and chirality) of the ligands as well as the reaction conditions. Diastereoselectivities observed in the catalytic hydrogenation of cyclic and acyclic ketones with the standard triphenylphosphane/ethylenediamine combination compare well with the best conventional hydride reductions. The use of appropriate chiral diphosphanes, particularly BINAP compounds, and chiral diamines results in rapid and productive asymmetric hydrogenation of a range of aromatic and heteroaromatic ketones and gives a consistently high enantioselectivity. Certain amino and alkoxy ketones can be used as substrates. Cyclic and acyclic alpha,beta-unsaturated ketones can be converted into chiral allyl alcohols of high enantiomeric purity. Hydrogenation of configurationally labile ketones allows for the dynamic kinetic discrimination of diastereomers, epimers, and enantiomers. This new method shows promise in the practical synthesis of a wide variety of chiral alcohols from achiral and chiral ketone substrates. Its versatility is manifested by the asymmetric synthesis of some biologically significant chiral compounds. The high rate and carbonyl selectivity are based on nonclassical metal-ligand bifunctional catalysis involving an 18-electron amino ruthenium hydride complex and a 16-electron amido ruthenium species.

1,630 citations

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606 citations

Journal ArticleDOI
TL;DR: The palladium-catalyzed cross-coupling reaction between different types of organoboron compounds, sp 2 -, sp 3 -, and sp-hybridized carbon-boron compounds and various organic electrophiles in the presence of base provides a powerful and general methodology for the formation of carbon-carbon bonds.

356 citations