Acylpalladium derivatives substitution

Oxidative carbonylation of alkenes is a unique reaction of Pd(II). Three types of oxidative carbonylation to give -substituted acid derivatives 130, a, -unsaturated esters 132 and succinate derivatives 134 are known, which can be understood by the following mechanism. Palladation of alkenes with PdX2, followed by CO insertion, generates the acylpalladium intermediate 129 whose reductive elimination affords -substituted carboxylic acid derivatives 130 (path a). Reaction in alcohol in the presence of a base starts by the formation of the alkoxycarbonylpalladium 128. Carbopalladation of alkene with 128 generates 131. Then y3-H elimination of the intermediate 131 yields the a-unsaturated ester 132 (path b). Further CO insertion to 131 gives the acylpalladium intermediate 133 and its alcoholysis yields the succinate derivative 134 (path c). Formation of the jS-alkoxy ester 130 (X-OR) is regarded as nucleophilic substitution of Pd-X in 131 with alcohols. 

Moreover, in the past 10 years, a number of works involving a nucleophilic attack of a nitrogen nucleophile over an acylpalladium intermediate, generated in situ from simple and easily prepared starting compounds, has been reported to be dealing with the synthesis of heterocyclic compounds, that is, 2,3,4,5-tetrahydro-lH-2,4-benzodi-azepine-l,3-dione derivatives 30 [39], tetrahydro-P-carboline/tetrahydriisoquinoline fused 5-lactam derivatives 31 and 32, respectively [40], and substituted hydantoins 33 [41] (Scheme 13.14). 

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