Ketones coupling

Ketones, coupling reactions of aryl halides with, 487-489 k-factor, 244 Kinetic studies, 73 Kumada coupling, 467, 489, 491... 

Coupling of carbonyl compounds with alkenes.6 In the presence of Sml2, aldehydes and ketones couple with electron-deficient alkenes to form y-lactones. An alcohol functions as the essential proton donor. 

The stannylation of conjugated ethylenic ketones coupled with an oxidative destanny-lation provided the synthetic means to various new carbonyl compounds (equations 207 and 208)106. 

The cyclization of a ketoamide illustrates one of the most versatile syntheses of 2,3-disubsti-tuted indoles. The mechanism underlying these reactions corresponds exactly to that of the ketone/ketone coupling in Figure 17.58. 

Cross-coupling reactions of ArCOAr. Reaction of Yb(0) with diaryl ketones changes the reactivity of the carbonyl group from electrophilic to nucleophilic. Thus in the presence of this lanthanoid metal, diaryl ketones couple with other ketones, nitriles, and epoxides to give pinacols, a-hydroxy ketones, and 1,3-diols, respectively, via the intermediate a. 

Sml2 can effectively promote the intermolecular reductive dimerisation of aldehydes or ketones giving rise to symmetrical diols.7 9 Generally, arylalde-hydes and aryl ketones couple within seconds in THF at room temperature. Aliphatic aldehydes and ketones react considerably more slowly several hours are required for the aldehydes, whereas for ketones reaction times of 24 h are usually needed. Nevertheless, these slower couplings can be greatly accelerated by the addition of additives such as HMPA.10... 

Diarylbutane-ly4-diones, Silyl enol ethers of aryl methyl ketones couple in the presence of C6H5IO-BF3 etherate (1 3) in CH2CI2 or ether to give 1,4-diarylbutane-l,4-diones in moderate yield. 

Reichwein, J. F., Pagenkopf, B. L. New Mixed Phosphonate Esters by Transesterification of Pinacol Phosphonates and Their Use in Aldehyde and Ketone Coupling Reactions with Nonstabilized Phosphonates. J. Org. Chem. 2003, 68,1459-1463. 

Pierce, K. G., Barteau, M. A. Ketone Coupling on Reduced Ti02 (001) Surfaces Evidence of Pinacol Formation. J. Org. Chem. 1995, 60, 2405-2410. 

As with the mono-ketones, coupling between groups on opposite sides of the carbonyl carbon is usually not observed. Similarly, coupling across the enolized carbonyl group (-C(OH)=CH) is not observed. 

Several versions of palladium-catalyzed coupling reactions have been used to convert o-nitroaryl halides to o-nitrophenylacetaldehydes or o-nitrobenzyl ketones. Coupling with trimethylsilylethyne gives aryl alkynes which can be converted to o-nitrophenylacetaldehyde enol ethers by sodium ethoxide (Scheme 21) <86CPB2362>. 

This operation, which needs at least two internal recycles, may be economic for special purposes (e.g., highly prized applications) such as enzyme-catalyst conversions. Indeed, it has been tested for the ADH-catalyzed reduction of hydrophobic ketones coupled with regeneration of the cofactor NADH. Another possibility discussed recently is the use of surface polarity-modified (heterogeneous) catalysts and their distribution between two immiscible solvents which occurs against gravity [8]. 

Titanium (iv) chloride with zinc in pyridine has been found to couple ketones reductively to afford symmetrical tetrasubstituted ethenes. Unsymmetrical alkenes can be synthesized in useful yields by titanium-induced ketone coupling if the less reactive component is used in excess. Cycloalkenes (ring size 4—16) are prepared in good yield by intramolecular coupling of the corresponding alkanedione. ... 

Silyl and geimyl functionalised vinyl cyclopropenes ring-open thermally to give allene and alkyne derivatives with the former dominating, a-trimethylsilyl a-allenyl ketones couple to give enediynes related to the neocarzinostatin chromophore and also result fnnn Y-(t-BuMe2Si)allenylborane and acetylenic aldehydes. Allenylsilanes couple with AdQ and... 

Alkyne replacements have also been reported. In 2008, Sakai et al. described the use of alkynylsilanes instead of terminal alkynes in the Cu-catalyzed synthesis of propargyl-amines, which was applicable to both secondary and primary aliphatic amines, although the latter afforded the corresponding products in low yield [145]. Very recently. Van der Eycken et al. applied the A -coupling to the C—H alkylation of azoles through a copper-catalyzed hetero-arene-amine-aldehyde/ketone coupling [146]. This reaction is proposed to proceed through the initial condensation of... 

D. D. Vachhani, A. Sharma, E. Van der Eycken, Angew. Chem. Int. Ed. 2013, 52, 2547-2550. Copper-catalyzed direct secondary and tertiary C-H alkylation of azoles through a heteroarene-amine-aldehyde/ketone coupling reaction. 

Catalyst Gold nano-particles (immobilized in aluminum oxyhydroxide support) [Au/A10(0H)] Keywords Alcohols, toluene, oxygen (ballon), room temperature, Au/A10(0H), oxidation, ketones, coupling... 

In the presence of [Cu(acac)2], a,6)-bisdiazo-ketones couple intramolecularly with the loss of nitrogen to give cycloalk-2-ene-l,4-diones [equation (16)]." ... 

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