Gold complexes asymmetric catalysis

Ferrocenylphosphine-gold complexes, 225 Formaldehyde oligomerization, 332 Formic acid, transfer hydrogenation, 123 Formulas, chiral compounds, xiii-xvii Four-dimensional chemistty. See Asymmetric catalysis... 

In 2010, Wang et al. applied the gold(I)/chiral Brpnsted acid relay catalysis to a novel three-component cascade reaction, providing direct access to structurally diverse julolidine derivatives 374 in high optical purity (Scheme 2.99). The phosphoric acid (Se)-catalyzed asymmetric Povarov reaction of 2-(2-propynyl)anihnes 365, (V-vinylcarbamate 8, and aldehydes 3 provided enantioenriched tetrahydroquinoline intermediates 372, which then underwent a hydroamination reaction under the catalysis of a gold complex to give julolidine derivatives with up to >99% ee [133]. 

Han Z-Y, Xiao H, Chen X-H, Gong L-Z. Consecutive intramolecular hydroamination/asymmetric transfer hydrogenation under relay catalysis of an achiral gold complex/chiral brpnsted acid binary system. J. Am. Chem. Soc. 2009 131 9182-9183. 

As seen from the examples assembled in Scheme 16.22 [27], gold catalysis has proven to be a powerful synthetic tool not only for the generation of molecular diversity but also for the creation of structural complexity [8k], From easily accessible substrates, especially linear derivatives, it is indeed possible to generate in a rapid, selective, and elHcient manner several new cycles and/or asymmetric centers. Notably, the compounds shown in Scheme 16.22 would not be so easily obtained using more traditional synthetic methods. 

The synthetic potential of gold catalysis, more especially for the generation of structural complexity, is particularly well illustrated by the total syntheses of Englerin A and B, reported independently in 2010 by Echavarren et al. and Ma et al. [31] (Scheme 16.26). A very similar approach was used by these two groups to produce, via a gold-catalyzed [2+ 2-1-2] intramolecular cycloaddition between an alkyne, an alkene, and a ketone, the core structure of the Englerins. Notably, this complex gold-catalyzed sequence, which operates with an absolute control of the stereoselectivity, allowed the creation of three new asymmetric centers and three new bonds (2 C-C and 1 C-O bonds). 

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