Gold, catalysis

Hashmi,A.S.KandHutohiiig, G.J. (2006) Gold catalysis. Angewandte Chemie International Edition, 45, 7896 ... 

Weyrauch, J.P., Wolfe, M., Prey, W. and Bats, J.W. (2005) Gold catalysis proof of arene oxides as intermediates in the phenol synthesis. Angewandte Chemie International Edition, 44, 2798. 

Rudolph, M. and Kurpejovic, E. (2004) Gold catalysis the benefits of N and N,0 ligands. Angewandte Chemie International Edition, 43, 6545. 

Gorin, D.J. and Toste, F.D. (2007) Relativistic effects in homogeneous gold catalysis. Nature, 446, 395-403. 

Burks, R. (2007) The Riches Of Gold Catalysis. Chemical ei Engineering News, Sept. 24, 87-91. 

Thompson, D. (1999) New Advances in Gold Catalysis Part II. Gold Bulletin, 32, 12-19. 

Bond, G.C. and Thompson, D.T (1999) Catalysis by Gold. Catalysis Reviews-Science and Engineering, 41, 319-388. 

Metal oxides of variable oxidation state as supports or support modifiers [202] are well known in gold catalysis. In the previous section we have already indicated some metal-support interactions influencing the electronic state of gold nanoparticles as well as the metallic or ionic state of gold. Of the numerous literatures we have to mention Haruta and Date [169], Bond [195], as well as Goodman works [186,203]. Further results can be found on the iron oxide system in recent literatures [162,204]. 

Haruta M. 1997. Size- and support-dependency in the catalysis of gold. Catalysis Today 36 153-166. 

D. T. Thompson, Perspective on industrial and scientific aspects of gold catalysis, Appl. Catal. A 243(2), 201-205 (2003). 

Tertiary N-butynylamine 48 when oxidized generates an N-oxide intermediate that is cyclized in situ via gold catalysis to give bicyclic piperidone 49 (09JA8394). As amine 48 can be prepared readily, the overall transformation constitutes a formal [4+2] synthesis. 

Thanks to a recent renaissance in gold catalysis, new gold-mediated transformations are being discovered with ever-increasing frequency. Some of these discoveries have been attributed to the action of gold vinylidenes. Fiirstner and coworkers uncovered one such example while screening catalysts for intramolecular alkyne hydroarylation (Scheme 9.23) [46]. 

The oxidation of propene to propene oxide is considered an essential practice in industrial chemistry [1]. Haruta et al. showed that this process can be led by heterogeneous catalysis with gold supported over titania [15, 16]. Another goal in the gold catalysis sequence is the selective oxidation of some alcohols and carbohydrates with molecular oxygen, as studied by Prati and Rossi [17]. 

Krause et al. worked on the conversions of 2-hydroxy-3,4-dienoates in the corresponding tri- and tetrasubstituted 2,5-dihydrofuranes by treatment with HCl gas in chloroform. Since this reaction was not accessible with acid-labile substrates [30,31], these conversions were tested through gold catalysis, obtaining better reaction rates and transformations in more difficult substrates compared to the well-established Ag(I)-promoted method [32]. 

Che et al. recently applied gold catalysis to the synthesis of lactams by the intramolecular addition of P-ketoamide to unactivated alkenes, as shown in Equation8.27 [83]. 

Hydrochlorination of Alkynes When Thomas and coworkers treated different alkynes in aqueous methanol with HAuC14 and observed the corresponding ketones as major products (Equation 8.28), with less than 5% of methyl vinyl ethers and vinyl chlorides, they were unaware of the fascinating treasure that was in front of them. Some of the most important types of products for gold catalysis were reported in the aforementioned study, but unfortunately at that time this process was believed to be a gold(III) oxidation process, despite the fact that the reaction achieved almost six turnovers. 

This was the first time that anyone stated that gold catalysis is an area worthy of further research [85]. 

The reaction worked with both internal and terminal alkynes (except silylated alkynes) and in many solvents, even in the neat alcohol added [105]. The mechanism proposed involved two catalytic cycles first, gold catalysis would lead to dihydro-furan by a fast intramolecular reaction then, the subsequent slower intermolecular reaction would be produced by the addition of alcohol to the enol ether to deliver a ketal (Scheme 8.18). 

Hashmi et al. also applied gold catalysis to the isochromene derivatives. This paper also reported a benzylic C-H activation that provided unprecedented dimerization from the formation of eight new bonds [110]. 

Dyker et al. reported an effective combination of an Ugi four-component reaction and gold catalysis to build highly functionalized isoindoles and dihydroisoquinolines with relatively good stereoselectivity [116] (Scheme 8.21). 

Floreancig and Hood recently incorporated gold-catalyzed heterocycle formation in the total synthesis of (+)-Andrachcinidine, a natural component extracted from the plant Andrachne aspera, which has medicinal properties. Gold catalysis was required in the last step of the synthesis, as shown in Scheme 8.22 [119]. 

Through a combination of experimental and theoretical calculations, Corma and coworkers proposed a mechanism for the hydrogenation of oleftnic molecules by gold catalysis. In this study, Au(III)-Schiffbase complexes proved to be as active as the corresponding Pd complexes. Some gold(III) intermediate species were proposed but were not detected [192]. 

The special nature of gold chemistry and gold catalysis is now known and many applications can be based on the low-temperature activity of supported gold compared to that of other metals [196]. 

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