Time filter

Source Type

Nolan S.P.,University of St. Andrews | Clavier H.,CNRS Institute of Molecular Sciences of Marseilles
Chemical Society Reviews | Year: 2010

Over the past decade, ruthenium-mediated metathesis transformations, including polymerization reactions, cross-metathesis, ring-closing metathesis, enyne metathesis, ring-rearrangement metathesis, and also tandem processes, represent one of the most studied families of organic reactions. This has translated into the development of a large number of structurally diverse catalysts. Whereas most of these investigations are focused on determining catalytic performance, only rare examples of studies dealing with chemoselectivity have been reported to date. Usually, variations are observed in product conversions but rarely in product distributions. In this critical review, we provide an overview of the stereochemistry of newly formed C=C bonds either in ring-closing or cross-metathesis as a function of the catalyst structure. A discussion of disparities encountered in macrocyclisation reactions leading (or not) to the formation of dimeric products is also presented. Since distinctive metathesis products could be isolated as a function of the ligand borne by the ruthenium centre - phosphine or N-heterocyclic carbene in the dissymetrization of trienes, enyne metathesis and ring rearrangements, these topics are also discussed (72 references). © 2010 The Royal Society of Chemistry. Source

Clavier H.,University of St. Andrews | Clavier H.,CNRS Institute of Molecular Sciences of Marseilles | Nolan S.P.,University of St. Andrews
Chemical Communications | Year: 2010

Electronic and steric ligand effects both play major roles in organometallic chemistry and consequently in metal-mediated catalysis. Quantifying such parameters is of interest to better understand not only the parameters governing catalyst performance but also reaction mechanisms. Nowadays, ligand molecular architectures are becoming significantly more elaborate and existing models describing ligand sterics prove lacking. This review presents the development of a more general method to determine the steric parameter of organometallic ligands. Two case studies are presented: the tertiary phosphines and the N-heterocyclic carbenes. © The Royal Society of Chemistry 2010. Source

Alphand V.,CNRS Institute of Molecular Sciences of Marseilles | Wohlgemuth R.,Sigma-Aldrich
Current Organic Chemistry | Year: 2010

The knowledge about these Baeyer-Villiger monooxygenases has grown tremendously since the first discovery and fundamental progress in the understanding of structure, function, substrate specificities and other enzyme properties has been facilitated by the development of recombinant biocatalysts. Nature uses these biocatalysts in aerobic biodegradation pathways of cyclic and acyclic ketones and in the biosynthetic pathways of natural products. The excellent performance of Baeyer-Villiger monooxygenases in nature for the catalysis of Baeyer-Villiger oxidations with high chemo-, regio- and enantioselectivity is a role model for sustainable catalytic Baeyer-Villiger oxidations in organic synthesis. A broad range of biocatalytic conversions of cyclic ketones to lactones, linear ketones to esters, sulfoxidations and other oxidations is described. Applications in dynamic kinetic resolution as well as process and scale-up issues have been important in making this reaction platform attractive to industrial scale Baeyer-Villiger oxidations. New discoveries of Baeyer-Villiger monooxygenases in biosynthesis are promising for highly selective oxidations. © 2010 Bentham Science Publishers Ltd. Source

Ibrahim-Ouali M.,CNRS Institute of Molecular Sciences of Marseilles
Tetrahedron Letters | Year: 2010

The first total synthesis of 11-tellura steroids was achieved via an intramolecular Diels-Alder cycloaddition of o-quinodimethanes as the key step. © 2010 Elsevier Ltd. Source

Pellissier H.,CNRS Institute of Molecular Sciences of Marseilles
Advanced Synthesis and Catalysis | Year: 2011

While tremendous advances have been made in asymmetric synthesis, the resolution of racemates is still the most important industrial approach to the synthesis of chiral compounds. The use of enzymes for the kinetic resolution (KR) of racemic substrates to afford enantiopure compounds in high enantioselectivity and good yield has long been a popular strategy in synthesis. However, transition metal-mediated and more recently organocatalyzed KRs have gained popularity within the synthetic community over the last two decades due to the progress made in the development of chiral catalysts for asymmetric reactions. Many catalytic non-enzymatic procedures have been developed providing high enantioselectivity and yield for both products and recovered starting materials. Indeed, the non-enzymatic KR of racemic compounds based on the use of a chiral catalyst is presently an area of great importance in asymmetric organic synthesis. The goal of this review is to provide an update on the principal developments of catalytic non-enzymatic KR covering the literature since 2004. This review is subdivided into seven sections, according to the different types of compounds that have been resolved through catalytic non-enzymatic KR, such as alcohols, epoxides, amines, alkenes, carbonyl derivatives, sulfur compounds and ferrocenes. Abbreviations: Ac: acetyl; acac: acetylacetone; AQN: anthraquinone; Ar: aryl; Atm: atmosphere; BINAM: 1,1′-binaphthalenyl-2,2′-diamine; BINAP: 2,2′- bis(diphenylphosphanyl)-1,1′-binaphthyl; BINEPINE: phenylbinaphthophosphepine; BINOL: 1,1′-bi-2-naphthol; Bmim: 1-butyl-3-methylimidazolium; Bn: benzyl; Boc: tert-butoxycarbonyl; Box: bisoxazoline; BSA: bis(trimethylsilyl)acetamide; Bu: butyl; Bz: benzoyl; c: cyclo; CBS: Corey-Bakshi-Shibata; Cbz: benzyloxycarbonyl; COD: cyclooctadiene; COE: cyclooctene; Cy: cyclohexyl; Dba: (E,E)-dibenzylideneacetone; DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene; DCC: N,N′-dicyclohexylcarbodiimide; de: diastereomeric excess; DEAD: diethyl azodicarboxylate; Dec: decanyl; DHQD: dihydroquinidine; Difluorphos: 5,5′-bis(diphenylphosphino)-2,2,2′, 2′-tetrafluoro-4,4′-bi-1,3-benzodioxole; DIPEA: diisopropylethylamine: DKR: dynamic kinetic resolution; DMAP: 4-dimethylaminopyridine; DMSO: dimethyl sulfoxide; DNA: deoxyribonucleic acid; DOSP: N-(dodecylbenzenesulfonyl)prolinate; DTBM: di-tert-butylmethoxy; ee: enantiomeric excess; Et: ethyl; equiv.: equivalent; Fu: furyl; Hex: hexyl; HIV: human immunodeficiency virus; HMDS: hexamethyldisilazide; KR: kinetic resolution; L: ligand; LDA: lithium diisopropylamide; MAO: methylaluminoxane; Me: methyl; Ms: mesyl; MTBE: methyl tert-butyl ether; Naph: naphthyl; nbd: norbornadiene; NBS: N-bromosuccinimide; NIS: N-iodosuccinimide; Pent: pentyl; Ph: phenyl; Piv: pivaloyl; PMB: p-methoxybenzoyl; Pr: propyl Py: pyridyl; r.t.: room temperature; s: selectivity factor; Segphos: 5,5′- bis(diphenylphosphino)-4,4′-bi-1,3-benzodioxole; (S,S′,R,R′)- Tangphos: (1S,1S′,2R,2R′)-1,1′-di-tert-butyl-(2,2′)- diphospholane; TBS: tert-butyldimethylsilyl; TBDPS: tert-butyldiphenylsilyl; TCCA: trichloroisocyanuric acid; TEA: triethylamine; TEMPO: tetramethylpentahydropyridine oxide; THF: tetrahydrofuran; Thio: thiophene; Tf: trifluoromethanesulfonyl; TMS: trimethylsilyl; Tol: tolyl; Ts: 4-toluenesulfonyl (tosyl). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Discover hidden collaborations