Aryl enol esters bromide

PdBr2 with an ammonium bromide in NMP provides an active catalyst enabling the oxidative insertion into the aryl enol esters, which then undergo decarbonylative (with formation of... 

Vinylic and aryl halides can be used to vinylate or arylate carboxylic esters (but not ketones) by the use of NiBr2 as a catalyst. " However, ketones have been vinylated by treating their enol acetates with vinylic bromides in the presence of a Pd... 

Vinylic and aryl halides can be used to vinylate or arylate carboxylic esters (but not ketones) by the use of NiBr2 as a catalyst.1463 However, ketones have been vinylated by treating their enol acetates with vinylic bromides in the presence of a Pd compound catalyst.1464 Also as in 0-94, this reaction can be used to close rings.1465 In one example of this, rings have been closed by treating a diion of a dialkyl succinate with a l,cu-dihalide or ditosylate,1466, e.g. ... 

The palladium-catalysed -arylation of ester enolates with aryl bromides has been studied both experimentally and computationally. The effect of the ligand on the selectivity of the a/j9-arylation reactions of ortho- and mcta-bromofluorobenzenes has been described. While / -arylation was predominantly observed with 1-bromo-2-fluorobenzene for a range of biarylphosphine ligands, a-arylation was primarily observed with l-bromo-3-fluorobenzene. It has been shown that electronic factors play a major role in the a// -arylation selectivity, with electron-withdrawing substituents favouring 0-arylation. 

Arylacetate esters have been generated by coupling aryl bromides with stannyl enolates generated from silyl ketene acetals. 

Arylation and vinylation of lithium ester enolates. Addition of -butyllithium lo suspensions of nickeKlI) bromide in THF produces a species that catalyzes substitution of lithium e.ster enolates (prepared with LDA in THF at -78°) by aryl and vinyl halides with retention of configuration. Lithium enolates of a./j-unsaturated esters undergo substitution in this reaction at the y-position (last example). The mechanism of this reaction is not certain. ... 

The addition of n-butyl-lithium to a suspension of nickel bromide in THF forms a suitable catalyst for the reaction of the lithium ester enolate (36) with aryl or vinyl halides in good yield.The reaction occurs with clean retention of the stereo-... 

Palladium complexes derived from stericaUy encumbered electron-rich phosphines such as QPhos (362) are well-suited catalysts for the reaction of aryl bromides with zinc enolates of esters [259] or amides [260] and also of aryl chlorides with the Reformatsky reagents [261]. As exemplified with the efficient formation of 361 (Scheme 4.82), only mono-arylation is observed, and the... 

Simple amides and esters 116 were conveniently deprotonated by Zn(tmp)2 (tmp = 2,2,6,6-tetramethylpiperidinyl anion) to generate zinc enolates 117. The zinc enolates 117 were readily coupled with aryl bromides using typical palladium-catalyzed Negishi cross-coupling reactions to give arylketones 118. Enolates formed by this method were suitable for use in aldol reactions that tolerate base-sensitive functional groups. 

Photoinitiation is not the only access to this chemistry, e.g., cathodic induced reduction or the use of alkali metals or other inorganic reducing reagents are also possible, but irradiation often is advantageous for preparative purposes. Since this is a chain process, the use of low-power lamps or a low quantum yield initiation step are not necessarily a limitation. Due to the requirement of a fast cleavage at the radical anion stage, aryl halides are by far the most used reagents, in particular iodides and, to a lower extent, bromides. Nucleophiles are carbanions from sufficiently acidic hydrocarbons, e.g., 1, 3-diphenylindane, fluorene or triphenylmethane [35-37] or, more commonly enolates from ketones [38], esters [39], MA -dialkylamides [40], nitriles [41]. C-C bond formation is obtained also with phenoxide or naphthoxide anions [42,43]. A few representative examples of synthetic applications of the S l... 

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