Alkene-gold® complexes

Addition of Active Methylenes In the previous decade Cinellu et al. studied certain 1,3-dicarbonyl gold complexes and some applications in organic synthesis were subsequently proposed [78]. Intermolecular addition of activated methylene compounds to alkenes was developed by using AuCl3/AgOTf [79]. 

Only one paper has reported on catalytic asymmetric hydrogenation. In this study by Corma et al., the neutral dimeric duphos-gold(I)complex 332 was used to catalyze the asymmetric hydrogenation of alkenes and imines. The use of the gold complex increased the enantioselectivity achieved with other platinum or iridium catalysts and activity was very high in the reaction tested [195] (Figure 8.5). 

Bis(adamantylimido) compounds, with monomeric chromium(VI) complexes, 5, 348 Bis(alkene) complexes conjugated, Rh complexes, 7, 214 mononuclear Ru and Os compounds, 6, 401 -02 in Ru and Os half-sandwich rj6-arenes, 6, 538 with tungsten carbonyls and isocyanides, 5, 685 Bis(u-alkenylcyclopentadienyl) complexes, with Ti(II), 4, 254 Bis(alkoxide) nitrogen-donor complexes, with Zr(IV), 4, 805 Bis(alkoxide) titanium alkynes, in cross-coupling, 4, 276 Bis(alkoxo) complexes, with bis-Cp Ti(IV), 4, 588 Bis[alkoxy(alkylamino)carbene]gold complexes, preparation, 2, 288... 

Alkenes act as nucleophiles with alkynes in the presence of gold catalysts. In the most simple version of the reaction, enynes are converted with gold complexes or salts, and in the absence of nucleophiles, into rearranged dienes, cyclopropanated carbocycles, and/or bicyclic cyclobutenes. Depending on the length of the tether and the nature of the substituents, the olefin attack to the alkyne occurs in an endo or an exo fashion (equation 33). Besides, substitution at the alkene plays an important role on the regioselectivity of the nucleophilic attack. ... 

Abstract Progress in the field of metal-catalyzed redox-neutral additions of oxygen nucleophiles (water, alcohols, carboxylic acids, and others) to alkenes, alkynes, and allenes between 2001 and 2009 is critically reviewed. Major advances in reaction chemistry include development of chiral Lewis acid catalyzed asymmetric oxa-Michael additions and Lewis-acid catalyzed hydro-alkoxylations of nonacti-vated olefins, as well as further development of Markovnikov-selective cationic gold complex-catalyzed additions of alcohols or water to alkynes and allenes. 

The cycloisomerization of l, -enynes promoted by gold complex catalysts, are known to go through only the third pathway. This high selectivity is due to two main reasons (1) the fragment [AuL]" has only one vacant site, thus it can not coordinate simultaneously the alkyne and the alkene moieties, (2) oxidative addition processes are not facile for gold complexes [24, 157, 158]. In general, gold(I) complexes surpass the reactivity shown by platinum(ll) and other electrophilic metals for the reaction of enynes. ... 

This type of cyclopropanation reaction catalyzed by a gold(I) complex produced cyclopropylmethyl carbene complex 321, which is reactive toward external alkenes or nucleophiles. The reaction depended on the ligand of the gold complex as well as the substituted patterns of enyne compounds. Echavarren and coworkers reported a cyclopropanation reaction mechanism. The cyclopropane gold complex intermediates 322 and 323 were trapped by external alkenes to give cyclopropanes 324 and 325, respectively (Scheme 1.157) [227]. 

Alkene complexes Alkynyl complexes Ammine complexes Aqueous chemistry Arsine complexes Auranofin Auride ion Aurophilicity Binary compounds Bond lengths acetylacetonate complex alkyls and aryls ammine complexes carboxylates cyanide complexes dialkyl sulphide complexes dithiocarbamates to gold... 

Fig. 2.12 Silver, gold and platinum complexes with monodentate NHC ligands as catalysts for the diboration of alkenes and alkynes...

AuCl(alkene)] (alkene = m-cyclooctene. norbornene, CHf/o-dicyclopentadiene ) complexes have been obtained by reaction of [AuCl(CO)] with the alkene.2280,2281 The structure of [AuC1(Ci0H12)] shows the ligand //2-bonded to gold via the C=C bond in the norbornene ring and the molecules are associated into dimers through Au Au interactions.2281... 

Complexes of Alkenes, Alkynes, and Arenes with Gold Compounds 299... 

Reactions by Other Nucleophiles As in the case of the formal cycloadditions of alkenes to allyl cations, the addition of alkenes to gold(I)-activated allenes generates intermediates that determine which cycloaduct formed. Based on this hypothesis, Toste et al. recently developed enantiorich bicycle-[3.2.0] structures by [2+2]-cycloaddition reaction catalyzed by chiral biarylphosphinegold(I) complexes [51]. 

From the encouraging results obtained in the reactions of a series of gold(III) oxo complexes with olefins [56], Cinellu et al. tried to achieve the supposed oxametalla-cyclic intermediate, which had never been isolated before [25]. In the reaction of 8 and norbornene 56, if the - atoms were considered to be equivalents of coordinated water, and it was therefore possible to talk about the gold-catalyzed addition of water to an alkene. The metallaoxetane 58 was separated from the gold-alkene complex 57 and characterized by X-ray crystal structure analysis. The subsequent stoichiometric reaction yielded epoxide 59 (Scheme 8.5). 

A gold monohydride species was also suggested in the report by Ito and Sawamura et al. on the dehydrogenative silylation of alcohols by HSiEt3 and a diphosphine gold(I) complex. Reaction was selective for the silylation of hydroxy groups in the presence of alkyl halides, ketones, aldehydes, alkenes, alkynes and other functional groups [193]. 

Metal carbene and carbyne complexes can act as donors analogous to alkenes and alkynes. When gold is the acceptor such interactions can lead to dimetallacyclopropanes or dimetaUacy-clopropenes, as illustrated by the reaction (81).748... 

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