α-Diazo β-ketoesters and diketones react with cyclic acetals under Rh(II) catalysis to yield unprecedented polyoxygenated 8- and 9-membered rings in one pot. The reactions occur under mild conditions with yields up to 90%. A perfect regioselectivity is obtained, which can be rationalized through a mechanistic hypothesis that considers 1) the formation of an oxonium ylide, 2) its transformation into an unsaturated acyclic oxocarbenium electrophilic intermediate, and 3) an intramolecular nucleophilic attack in a direct application of Baldwin's rules.

The synthesis and characterization of a new class of cationic (NHC)gold(I) (NHC = N-Heterocyclic carbene) complex containing the phosphate counterions TRISPHAT and TRISPHAT-N have been achieved. The selection of the appropriate hexacoordinated phosphate architecture permits the isolation of complexes bearing an inner or outer sphere anionic counterion.

AbstractThe title reaction affords a rare type of 15‐membered polyether macrocycle.

[CpRu(CH(3)CN)(3)][PF(6)] and diimine ligands catalyze together the decomposition of α-diazocarbonyl compounds leading to O-H insertion and condensation reactions. In comparison with Rh(II) and Cu(I) complexes, the CpRu catalysts produce rapid and often more selective reactions. Promising enantioselectivities are obtained in dioxole syntheses.

Aufgeladen: Ein Aminophosphoniumkation, zwei Phenolmoleküle und ein Phenoxidanion organisieren sich zu einem cyclischen Netzwerk intermolekularer Wasserstoffbrücken. Dieses ladungsunterstützte reaktive System ist ein effektiver Katalysator für die konjugierte Addition von Azlactonen an α,β-ungesättigte Acylbenzotriazole (siehe Schema; Bt=Benzotriazol).

Charged up: An aminophosphonium cation, two phenols, and a phenoxide anion self-assemble in a cyclic network of intermolecular hydrogen-bonds. This charged-assisted reactive combination efficiently catalyzes the conjugate addition of azlactones to α,β-unsaturated acylbenzotriazoles.

Ru-based olefin metathesis complexes have been widely studied during the last twenty years with the discovery of various robust and efficient catalysts for this powerful synthetic transformation. However, complexes enabling to combine high activity, stability and recyclability still need to be quested. This article reports a short overview of several strategies concerning the Hoveyda-Grubbs boomerang type complexes devoted to finding an optimal compromise between these antinomic properties (e.g. the enhancement of catalyst activity and its recovery), leading in some cases to minimize both the catalyst loading and the ruthenium contamination in the metathesis products.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The application of chiral chelating hydroxy NHC in copper-catalyzed asymmetric allylic alkylation (Cu-AAA) involving various dialkylzincs and allylic phosphate substrates is reported here. From a library of 11 chiral chelating hydroxyalkyl NHC, a fine-tuning has been done to identify the best architectural features enabling to produce the expected g-adducts in total regioselectivity, good isolated yields, and excellent enantioselectivities (ranging from 93% to >98% ee).

The copper-catalyzed conjugate addition of Grignard reagents to 3-substituted cyclic enones allows the formation of all-carbon chiral quaternary centers. We demonstrate in this article that N-heterocyclic carbenes act as efficient chiral ligands for this transformation. High enantioselectivities (up to 96% ee) could be obtained for a variety of substrates.

AbstractThe carbene generated from NHC efficiently promotes the process.

Angewandte ChemieVolume 122, Issue 10 p. 1937-1937 VorschauFree Access Vorschau: Angew. Chem. 11/2010 First published: 22 February 2010 https://doi.org/10.1002/ange.201090026AboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume122, Issue10March 1, 2010Pages 1937-1937 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

The design and the synthesis of a set of new chiral hydroxyalkyl- and hydroxyaryl-chelating diaminocarbene ligands is reported. Comparative catalytic studies show the importance of the scaffold design around the NHC unit to obtain a high enantiocontrol in Cu-catalyzed asymmetric conjugate addition (ACA). Whereas low selectivities are observed when the stereogenic centre is placed within the N-heterocyclic ring, an interesting match effect can be observed when central chirality is located within both of the two side chains, which enables up to 92 % ee in the catalysis reaction. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The synthesis and characterization of three novel trifluoro-methylamido-conta-ming "boomerang" precatalysts bearing various N-heterocyclic carbene (NHC) ligands are reported. Comparative kinetic and stability studies show the significant effect of the NHC on the catalyst reaction profile. An investigation of the reaction scope for diverse metathesis transformations has allowed us to establish the influence of the NHC on catalyst activity, especially as a function of substrate steric bulk. The excellent stability of one of the novel precatalysts is disclosed, and allowed for its recovery at the end of catalytic reactions. Large-scale ring-closing metathesis, enyne-metathesis and cross-metathesis experiments have revealed the recoverability of the catalyst. ICP-MS analyses of the synthesized products reveal Ru contamination levels of less than 2.5 ppm. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Herein, we report the use of phosphinoazomethinylate salts as chiral efficient ligands for the copper-catalyzed asymmetric conjugate addition (ACA) of dialkylzinc to various enones. These tridentate P,N,O ligands are straightforwardly obtained in a one-step procedure from commercially available enantiopure α-aminoacids. Performing the conjugate addition in the greener AcOEt solvent, high enantioselectivities were reached for both cyclic and acyclic enones ranging between 72% to 98% ee and 96% to >99%, respectively. The 2/1 Cu/ligand ratio required to obtain high enantioselectivities, led us to envisage a copper–copper bi-metallic catalytic system for this transformation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Three novel "boomerang" precatalysts bearing different aminocarbonyl functions are reported. Comparative kinetic studies show that this functional group allows for a control of the catalytic activity in metathesis transformations. The scope of the more active catalyst is investigated and shows a good tolerance to various substrates in ring-closing metathesis, enyne metathesis, and cross metathesis. ICP-MS analyses illustrate the good affinity of this catalyst for silica gel, as levels of Ru contamination lower than 6 ppm are detected in the final products.

Whereas the boomerang ligand of Hoveyda-Grubbs pre-catalysts can be modified by attachment of a pyridinium tag to its benzylidene moiety, a precise adjustment of the length of the spacer allows the optimum balance to be reached between the activity of the catalyst and its recoverability, exceeding 98% after 6 catalytic runs in the best case.