Carbonylation gold-catalyzed

In the gold-catalyzed carbonylation of olefins according to Xu et al., gold(I) carbonyl complexes are considered as active catalysts this reaction proceeds already at room temperature in concentrated sulfuric acid at a CO pressure of 1 atm and leads after acid-catalyzed skeletal rearrangement to tertiary carboxylic acids such as 16,18, and 19 (Scheme 4) [11],... 

Carbonyl compounds also react with allenes and, in fact, the first example of a gold-catalyzed addition of a nucleophile to allenes was the formation of lurans from allenones. The reaction was applied by Gevorgyan to the synthesis of substituted furans and in the case of bromide-substituted allenes halide migration was observed. Similar additions of... 

Michael additions to conjugated carbonyls can be catalyzed by gold species. Among them, arene additions are the most studied area but other nucleophiles can attack the gold-coordinated enones as well. In fact, the intermolecular aza-Michael additions of carbamates to enones was reported in 2002 with both Au(I) and Au(III) salts, and in 2007 an intramolecular aUcoxide and amide conjugate addition has been developed and applied to the synthesis of (+)-andrachcinidine (equation 132). In the latter case, the enones are formed as intermediates in a previous gold-catalyzed step that is the hydration of an alkyne and methanol loss. Then the cyclization takes place to give piperidines. 

Examples of gold-catalyzed carbonylation of amines and olefins exist related to the activation of carbonyl. The first case involves the formation of carbamates from anilines and CO in the presence of alcohols or the production of acetamides from aliphatic amines. In these examples, Au(I) (usually [AuCl(PPh3)]) catalysts are preferred. For the carbonylation of olefins, gold(I) carbonyls are prepared in situ in sulfiu ic acid media to afford carboxyhc acids. ... 

Not only simple, unactivated olefins but also a,P-unsaturated carbonyl compounds undergo gold-catalyzed addition reactions. Electron-rich arenes or heteroarenes (e.g., indoles) are suitable carbon nucleophiles for these Michael additions. For the 1,4-addition of indoles to enones, enals, and related Michael acceptors, simple gold(III) catalysts like NaAuCl4-2 or AuCU can be used... 

Representative procedure for the gold-catalyzed intermolecular addition of 1,6-enynes to carbonyl compounds. Dimethyl 3-phenyltetrahydro-3H-cyclopenta[c]cyclopropa[b]furan-5,5(6H)-dicarboxylate ... 

In the total synthesis of (+)-lycopladine A by Toste et al. [30], a gold-catalyzed 5-endo cyclization of an iodoalkyne with a silyl enol ether has been used (Scheme 16.25). This transformation efficiently produces a -unsaturated bicyclic ketone that possesses the required quaternary asymmetric center at the position a to the carbonyl group. The vinyl iodide functionaiity generated during the cyclization was subsequently used in a palladium-catalyzed cross-coupling reaction in order to construct the pyridine ring of (-F)-lycopladine A. 

Another possibility would be the use of allylic esters, which after a gold-catalyzed cycloisomerization with the carbonyl oxygen atom as the nucleophile deliver activated allylic intermediates which at the same time contain a vinylgold substructure. After transfer of an allyl cation to palladium(O), an oxidative addition to palladium, the vinylgold intermediate could transfer the organic moiety to palladium(II). A final reductive elimination would close the catalytic cycle. At the same time, no halide that potentially could deactivate the cationic gold(I) catalyst would be present. Indeed, Blum et al. [30] presented such systems. But... 

The gold-catalyzed intermolecular addition of carbonyl compounds to 1,6-enynes is also feasible. This methodology leads to a wide range of compounds (Scheme 1.33) [229-231]. Thus, tricyclic compounds XLVII, the products of formal [2+2+2] cycloaddition XLVIII, 1,3-dienes XLIX or 1,3-dioxolanes L can be selectively synthesized by changing the substitution pattern at the alkene moiety and using different gold(l) complexes. Moreover, the intermolecular addition of carbonyl compounds to 1,5-enynes has also been reported [230]. 

Gold-Catalyzed Reactions of 1,5- and 1,6-Enynes with Carbonyl Compounds Cycloaddition vs. Metathesis... 

Schelwies, M., Dempwolff, A., Rominger, R, Hehnchen, G. (2007). Gold-catalyzed intermolecular addition of carbonyl compounds to 1,6-enynes. Angewandte Chemie - International Edition, 46, 5598-5601. 

The gold-catalyzed benzannulation of o-alkynylbenzaldehydes 11 proceeded not only with alkynes or alkenes, but also with carbonyl compounds 47 (Scheme 15.19) [32], The reaction proceeded even with conjugated enyne aldehydes 20. Paraldehyde 49 can be used as a masked acetaldehyde in this reaction. 

Asao et al. conducted a systematic smdy of gold-catalyzed intramolecular reactions by designing two types of substrates one a top-down approach, in which a carbon chain is attached to the carbonyl group, and the other a bottom-up approach, in which a carbon tether is extended from the alkynyl terminus [37]. As the former case, benzannulation of 59 proceeded smoothly with an AuBrs catalyst, and the corresponding tricyclic compounds 60 were produced. On the other hand, the reaction of 61 gave dihydrophenanthrenone derivatives 62 as the latter case (Scheme 15.25). 

The putative metal cationic intermediates can be interconnected into a series of cationic processes such as Friedel-Crafts, pinacol, Nazarov, Prins-type reactions. In Scheme 7.28, the gold-catalyzed cycloisomerization of 1,6-enynes is followed by an intramolecular nucleophilic attack by the proximate carbonyl to generate the tetrahydro-pyranyl cation, which participate in a Prins-type reaction to produce tricyclic compounds resembling the core structures of several terpenoids [52]. 

Several other rearrangements leading to the construction of complex scaffolds were developed with NHC-Au complexes as catalysts. More specifically, the gold-catalyzed intramolecular addition of an oxygenated functionality (carbonyl, epoxide, ether) on an alkyne has been largely employed to initiate various types of multi-step rearrangements [Scheme 11.17 and eqn (11.5)]. ... 

Jin T, Yamamoto Y. Gold-catalyzed synthesis of polycyclic enones from carbon tethered 1,3-enynyl carbonyls via tandem heteroenyne metathesis and Nazarov reaction. Org. Lett. 2008 10 3137-3139. 

Scheme 9 Proposed mechanism for the gold-catalyzed formation of a,P-unsaturated carbonyl compounds based on calculations...

The proposed reaction mechanism for the gold-catalyzed production of a,p-unsaturated carbonyl compounds based on calculations is presented below (Scheme 9). Gold(l) activates water by forming the hydroxide complex VII and... 

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