Aldol condensation gold

The first example of a C C bond-forming reaction catalysed by gold was the asymmetric aldol condensation developed in 1986.30 The addition of an isocyano acetate to an aldehyde produces the A -oxazole as the major and Z-oxazole as the minor product in excellent enantiomeric excess (ee) in the presence of a cationic gold catalyst, [Au(CyNC)2]BF4, and a chiral diphosphanyl ferrocene ligand (see Scheme 12.5). 

Transition-metal complexes bearing chiral ligands catalyze an asymmetric aldol condensation of isocyanoacetates with aldehydes to afford a mixture of cis- and /rons-4,5-disubstituted-4,5-dihydrooxazoles (188) in high optical purity (Equation (27)). Both gold and silver ferrocenylphos-phine complexes are effective <94TL2713>. 

N-methyl-6-hydroxy-amino acids, such as the amino acid MeBmt (32). The aldol condensation of aldehydes with isocyanoacetate in the presence of a chiral ferrocenylphosphine-gold(I) complex afforded... 

Triazolylidene gold complexes were exploited as precursors for highly active catalysts in the aldol condensation of aldehydes and isocyanides to form 2-oxazolines (13JA13193). 

In 2013, another intramolecular hydrosilojqrlation was combined with a Mukaiyama aldol condensation by Gong et al. in an enantioselective relay catalytic cascade. This domino reaction occurred between atylacetylene silanols and glyoxylates and was induced by a combination of an achiral gold catalyst and a chiral N-triflyl phosphoramide. As shown in Scheme 7.37,... 

It is interesting that aldol-type condensation of tosylmethyl isocyanide (16) with aldehydes is catalyzed by the silver catalyst more stereoselectively than that catalyzed by the gold catalyst under the standard reaction conditions (Scheme 8B1.9) [26], Elucidation of the mechanistic differences between the gold and silver catalysts in the asymmetric aldol reaction of 16 needs further study. Oxazoline 17 can be converted to optically active a-alkyl-p-(A-methyl-amino)ethanols. 

Asymmetric aldolization of a-isocyanoacetamide and fluorinated benzaldehydes has been realized with a gold(I) salt and a ferrocenyl amine-phosphine ligand. (Salen)-Ti complexes serve well in catalyzing the condensation of diketene with aldehydes. " A camphor lactam is an adequate chiral auxiliary as its derived imide undergoes asymmetric aldol reactions. 

TABLE 8B1.6. Gold-Catalyzed Aldol-I pe Condensation of (Isocyanamrtliyl)pliosplioiiate 12 with Aldehydes (Scheme 8B1.6)... 

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