Gold-catalyzed highly enantioselective synthesis of axially chiral allenes

Axially chiral allenes are synthesized from chiral propargylamines catalyzed by KAuCl4 in high yields (up to 93% yield) and excellent enantioselectivities (up to 97% ee) in CH3CN at 40 °C. The reaction has been applied to the synthesis of novel allene-modified artemisinin derivatives with the delicate endoperoxide moieties remaining intact. A tentative mechanism regarding gold(l)-catalyzed intramolecular hydride transfer was proposed on the basis of deuterium-labeling experiments and ESI-MS analysis of the reaction mixture. © 2008 American Chemical Society.link_to_subscribed_fulltex

Elevated catalytic activity of ruthenium(II)–porphyrin-catalyzed carbene/nitrene transfer and insertion reactions with N-heterocyclic carbene ligands

Bis(NHC)ruthenium(II)–porphyrin complexes were designed, synthesized, and characterized. Owing to the strong donor strength of axial NHC ligands in stabilizing the trans M[DOUBLE BOND]CRR′/M[DOUBLE BOND]NR moiety, these complexes showed unprecedently high catalytic activity towards alkene cyclopropanation, carbene C[BOND]H, N[BOND]H, S[BOND]H, and O[BOND]H insertion, alkene aziridination, and nitrene C[BOND]H insertion with turnover frequencies up to 1950 min−1. The use of chiral [Ru(D4-Por)(BIMe)2] (1 g) as a catalyst led to highly enantioselective carbene/nitrene transfer and insertion reactions with up to 98 % ee. Carbene modification of the N terminus of peptides at 37 °C was possible. DFT calculations revealed that the trans axial NHC ligand facilitates the decomposition of diazo compounds by stabilizing the metal–carbene reaction intermediate

Silver(i)-mediated highly enantioselective synthesis of axially chiral allenes under thermal and microwave-assisted conditions

Silver(i) salts mediated stereospecific transformation of optically active propargylamines to axially chiral allenes with excellent enantioselectivities (17 examples with 96-99% ee; one substrate with 91% ee) without subsequent racemization. © 2010 The Royal Society of Chemistry.link_to_subscribed_fulltex

Gold(III) salen complex-catalyzed synthesis of propargylamines via a three-component coupling reaction

Propargylamines have been synthesized by a gold(III) salen complex-catalyzed three-component coupling reaction of aldehydes, amines, and alkynes in water in excellent yields at 40 °C. With chiral prolinol derivatives as the amine component, excellent diastereoselectivities (up to 99:1) have been attained. This coupling reaction has been applied to the synthesis of propargylamine-modified artemisinin derivatives with the delicate endoperoxide moieties remaining intact. Cytotoxicities with IC 50 values up to 1.1 μM against a human hepatocellular carcinoma cell line (HepG2) were exhibited by these artemisinin derivatives. © 2006 American Chemical Society.link_to_subscribed_fulltex

Gold(III) (C^N) complex-catalyzed synthesis of propargylamines via a three-component coupling reaction of aldehydes, amines and alkynes

Propargylamines are synthesized in high yields via a gold(III) (C^N) complex-catalyzed three-component coupling reaction of aldehydes, amines and alkynes in water at 40 °C. Excellent diastereoselectivities (up to 99:1) have been achieved when chiral prolinol derivatives are employed as the amine component. Notably, the [Au(C^N)Cl2] complex (N^CH = 2-phenylpyridine) could be repeatedly used for 10 reaction cycles, leading to an overall turnover number of 812. © 2008 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Silver(I)-mediated highly enantioselective synthesis of axially chiral allenes under thermal and microwave-assisted conditions

The 12th Belgian Organic Synthesis Symposium (BOSSXII), Namur, Belgium, 11-16 July 2010

Selective functionalisation of saturated C-H bonds with metalloporphyrin catalysts

The recent surge of interest in metal-catalysed C-H bond functionalisation reactions reflects the importance of such reactions in biomimetic studies and organic synthesis. This critical review focuses on metalloporphyrin-catalysed saturated C-H bond functionalisation reported since the year 2000, including C-O, C-N and C-C bond formation via hydroxylation, amination and carbenoid insertion, respectively, together with a brief description of previous achievements in this area. Among the metalloporphyrin-catalysed reactions highlighted herein are the hydroxylation of steroids, cycloalkanes and benzylic hydrocarbons; intermolecular amination of steroids, cycloalkanes and benzylic or allylic hydrocarbons; intramolecular amination of sulfamate esters and organic azides; intermolecular carbenoid insertion into benzylic, allylic or alkane C-H bonds; and intramolecular carbenoid C-H insertion of tosylhydrazones. These metalloporphyrin-catalysed saturated C-H bond functionalisation reactions feature high regio-, diastereo- or enantioselectivity and/or high product turnover numbers. Mechanistic studies suggest the involvement of metal-oxo, -imido (or nitrene), and -carbene porphyrin complexes in the reactions. The reactivity of such metal-ligand multiple bonded species towards saturated C-H bonds, including mechanistic studies through both experimental and theoretical means, is also discussed (244 references). © 2011 The Royal Society of Chemistry.link_to_subscribed_fulltex

Gold-mediated bifunctional modification of oligosaccharides via a three-component coupling reaction

An efficient modular approach for single-site incorporation of two independent functionalities (amines and alkynes) into aldehyde-containing oligosaccharides concurrently by using a one-pot gold-mediated three-component coupling reaction in aqueous medium under mild conditions has been developed.link_to_subscribed_fulltex

Cyclometallated Gold(III) Complexes as Effective Catalysts for Synthesis of Propargylic Amines, Chiral Allenes and Isoxazoles

A series of cyclometallated gold(III) complexes [Au(CN)Cl2] 1a-l (HCN=arylpyridines) and a PEG-linked complex 1m were synthesized. Complexes 1a-m are effective in catalyzing the synthesis of propargylic amines, chiral allenes and isoxazoles. Six-membered ring cyclometallated gold(III) complexes 1f-l exhibited higher catalytic activity than five-membered ring cyclometallated gold(III) complexes 1a-e. The diastereoselectivity of propargylic amines could be tuned by using chiral aldehyde and/or amine substrates. Excellent enantioselectivities (90-98% ee) were achieved in chiral allene synthesis. Chiral allene racemization could be minimized by using 1f as catalyst. The PEG-linked catalyst 1m is the most catalytically active towards synthesis of propargylic amines, in which case a product turnover of 900 was achieved. Moreover, 1m could be repeatedly used for 12 reaction cycles, leading to an overall turnover number of 872.Department of Applied Biology and Chemical Technolog

Luminescent ruffled iridium(iii) porphyrin complexes containing N-heterocyclic carbene ligands : structures, spectroscopies and potent antitumor activities under dark and light irradiation conditions

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