Allylic carboxyl group palladium catalyzed

Although nucleophiles generally substitute allylic leaving groups with retention of configuration, the substitution of allylic carboxylates sometimes proceeds in a nonstereospecific manner due to palladium-catalyzed isomerization of the substrates (Scheme 48). ... 

The research group of Muzart and Henin studied extensively the palladium-catalyzed EDP of allyl- or benzyl-carboxylated compounds. Mainly two types of substrates, prochiral enol carbonates A and racemic (3-keto esters B, were used to afford enols C as transient species [25]. In the presence of a chiral proton source, asymmetric protonation/tautomerization of enols led to enantioenriched ketones D... 

The carbonylation of allylic compounds by transition metal complexes is a versatile method for synthesizing unsaturated carboxylic acid derivatives (Eq. 11.22) [64]. Usually, palladium complexes are used for the carbonylation of allylic compounds [65], whereas ruthenium complexes show characteristic catalytic activity in allylic carbonylation reactions. Cinnamyl methyl carbonate reacts with CO in the presence of a Ru3(CO)i2/l,10-phenanthroline catalyst in dimethylformamide (DMF) to give methyl 4-phenyl-3-butenoate in excellent yield (Eq. 11.23) [66]. The regioselectivity is the same as in the palladium complex-catalyzed reaction. However, when ( )-2-butenyl methyl carbonate is used as a substrate, methyl ( )-2-methyl-2-butenoate is the major product, with the more sterically hindered carbon atom of the allylic group being carbo-nylated (Eq. 11.24). This regioselectivity is characteristic of the ruthenium catalyst [66]. 

After these initial results by Tsuji, this elementary step was incorporated into a catalytic process by Hata and co-workers at Toray Industries and by Atkins and co-workers at Union Carbide. These groups reported reactions of allylic phenyl ethers, allylic alcohols, and allylic acetates with carboxylates, alcohols, primary and secondary amines, and methyl acetoacetate catalyzed by Pd(0) complexes and precursors to Pd(0) complexes (Equation 20.3). - After these initial reports, early developments focused on reactions of "soft" carbanions derived from 3-dicarbonyl compounds, cyanoesters, and related compounds containing two electron-withdrawing groups attached to the nucleophilic carbon. Although these reactions occur with allylic halides in the absence of a catalyst, these reactions are greatly accelerated by palladium catalysts. Thus, the palladium catalyst allows these reactions to occur under mild conditions with allylic acfetates, which are more accessible than allylic halides, and with selectivities that are altered by the metal catalyst. 

A variety of 3-vinyl-substituted imidazo[l,5-a]indole derivatives were synthesized by intramolecular Pd catalyzed cyclization of the indole-2-carboxylic acid al-lenamides through either a domino carbopalladation/exo-cyclization process or a novel hydroamination reaction that proceeds smoothly under microwave irradiation. Both the observed pathways involve a Tu-allyl-palladium (II) complex arising from insertion of the allene group into a palladium (II) species, the latter being formed in situ by the intervention of an aryl iodide or of the N-H group. In both these cases, the role of nucleophile is covered by the indole nitrogen (Beccalli et al., 2010). 

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