Palladium : allylation with

The hydrolytic DKR of allyl esters has been studied as a DKR of esters. The first DKR was accomplished through Pd-catalyzed racemization and enzymatic hydrolysis of allylic acetates in a buffer solution. However, the DKR under these conditions was limited to cyclohexenyl acetates to give symmetrical palladium-allyl intermediates. Among them, 2-phenyl-2-cyclohexenyl acetate 9 was the only substrate to have been resolved with good results (81% yield, 96% ee). 

There are few reports of oxidative addition to zerovalent transition metals under mild conditions three reports involving group 10 elements have appeared. Fischer and Burger reported the preparation of aTT -allylpalladium complex by the reaction of palladium sponge with allyl bromide(63). The Grignard-type addition of allyl halides to aldehydes has been carried out by reacting allylic halides with cobalt or nickel metal prepared by reduction of cobalt or nickel halides with manganese/iron alloy-thiourea(64). 

A wide variety of organoalkynyl derivatives of cotarnine hydrochloride, a cyclic iminium salt with rich biological activity, were prepared from the direct alkynylation of cotarnine hydrochloride using silver(l) alkynyls.180 Substituted enynes were prepared from the coupling reactions of silver alkynyls with the palladium allyl intermediates, which was... 

Platinum-catalyzed allylation of aldehydes with allyltin reagents was first reported in 1995.4S7 457b,483 483a Ar0matiC) aliphatic, a,/3-unsaturated aldehydes and even cyclohexanone undergo allylation with allyltributyltins in the presence of PtClgtPP 113)2 >n THF at room temperature or higher temperature (Equations (123) and (124)). Allylplatinum species are considered to be the active intermediates on the basis of related mechanistic studies on palladium catalysis. 

Structural Identification of a Palladium Complex with a Chiral Sulfoxide Ligand Used in Asymmetric Palladium-Catalyzed Allylic Alkylations... 

The mechanism of this reaction was considered on the basis of hydropalladation (Scheme 14). To minimize steric repulsions, the palladium hydride complex approaches the C=CH2 moiety of the allene in the anti-Markovnikov mode from the opposite side of the substituent. This addition gives a 7t—allyl palladium complex with the (Z)-configuration,18 which is converted to the (Z)-product by C-P bond formation, with regeneration of the Pd(0) catalyst. 

For further details of this reaction, the reader is referred to Chapter 9. The catalytic allylation with nucleophiles via the formation of Ti-allyl metal intermediates has produced synthetically useful compounds, with the palladium-catalyzed reactions being known as Tsuji-Trost reactions [31]. The reactivity of Ti-allyl-iridium complexes has been widely studied [32] for example, in 1997, Takeuchi idenhfied a [lrCl(cod)]2 catalyst which, when combined with P(OPh)3, promoted the allylic alkylation of allylic esters 74 with sodium diethyl malonate 75 to give branched... 

Using a similar approach, Chechik and Crooks (73), modified the PAMAM dendrimer-encapsulated palladium nanoparticles with perfluoropolyether tails utilizing non-covalent ion-pair interactions. The catalytic hydrogenation of six substrates under biphasic conditions (toluene/ perfluoro-2-butyltetrahydrofuran FC-75) was investigated. Allyl alcohol, methyl acrylate, vinyl isopropenyl ether, and... 

PdCl(7r-C3H5)]2 is reported to exist in two forms (163), i.e., the yellow or a-form described above, and a dark green or /3-form prepared by reacting palladium chloride with an acidified aqueous solution of allyl alcohol below 10° at 15° the product is the yellow a-form (163). Isomerization of this type has not been reported for other 7r-allylicpalladium complexes. 

Polystyrene-bound secondary aliphatic amines and /V-alkyl amino acids can be ally-lated by treatment with a diene and an aryl iodide or bromide in the presence of palla-dium(II) acetate (Entry 14, Table 10.3). As the diene, 1,3-, 1,4-, and 1,5-dienes can be used, and, besides aryl halides, heteroaryl bromides have also been successfully used [63], This remarkable reaction is likely to proceed via the formation of an aryl palladium complex, with subsequent insertion of an alkene into the C-Pd bond. The resulting organopalladium compound does not undergo ( -elimination (as in the Heck reaction), but isomerizes to an allyl palladium complex, which reacts with the amine to give the observed allyl amines. 

Metal-n-allyl complexes are important in a number of stereoselective catalytic reactions and are therefore attractive for computational chemists (see also Chapter 13, Section 13.2). An empirical force field study based on the MM2 parameterization scheme aimed at predicting stereoselective nickel(0)-catalyzed cycloadditions was recently conducted 56. As in a similar study 57, where a force field for the structure optimization of palladium-allyl systems was developed, dummy atoms were needed to define the structural model. Based on the assumptions required to model a catalytic process, the results obtained have to be interpreted with caution. 

Esters of allylic alcohols with resin-bound carboxylic acids can be converted into palladium allyl complexes by treatment with palladium(O). These allyl complexes react with carbon... 

Direct allylation of rhodanine 49 (Scheme 13) under Pd(0)-catalysis with cinnamyl ethyl carbonate affords the /V-allylated compound 50. However, allylation with cinnamyl bromide and a base is not regioselective, producing a mixture of 50 and sulfide 51. Sulfide 51 isomerizes to 50 under palladium catalysis (N > S), thus indicating that Pd(0)-catalyzed allylation of 49 is thermodynamically controlled (93T1465). 

When imidazole 67 is allylated with glycoside 74 (Scheme 17), product 75 is the only isolated compound, as reported by Sinou and co-workers (92TL2481). Again, the nonsymmetrical palladium intermediate is attacked at the less hindered point, but in this case, this point is, at the same time,... 

Abstraction of chloride from a vinylpalladium complex by silver acetate has been reported,45 as well as halide abstraction by silver triflate from arylpalladium halides.46 More interestingly in the context of creating C-C bonds, silver perchlorate was able to promote the reaction of (r -aryl)palladium bromide with dienes. Silver-promoted bromide abstraction led to the formation of (r 1-r 2-enyl)palladium complexes, which evolved further through the regioselective formation of a C-C bond between the aryl group and the former diene. Reactions with nonconjugated dienes suggested that the reaction proceeds via carbometallation of the less crowded double bond. Isomerization and (3 elimination led to a (ri3-allyl)palladium complex (Scheme 10.26).47... 

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