Intermolecular reactions acylpalladation

The intennolecular acylpalladation corresponds to the addition of an acyl-palladium bond onto a rr-bond system of another molecule this elementary step can also be referred to as an insertion (Scheme I). This produces another organopalladium complex, which can in principle participate in subsequent propagation or termination reactions. This excludes processes that involve alkoxycarbonylation (R— = R O—) and hydrocarbonyla-tion (R— = H—). This section will focus on nonpolymeric intermolecular reactions of acylpalladium complexes with different 7r-bond systems (alkenes, imines, dienes, and alkynes). 

The relative rates of carbopalladation and CO insertion represent a very delicate issue, which is, to a considerable extent, dependent on the reaction conditions. The reaction of Phi with even 1 attn of CO in the presence of 1-octyne and MeOH under the influence of 5 mol % of Cl2Pd(PPh3)2 gives only methyl benzoate (73%) without the sign of either intermolecular carbopalladation or acylpalladation. One may conclude that inter-molecular C—Pd and Ac—Pd processes are, in general, decidedly slower than the CO insertion-methanolysis tandem process. 

As in the cases of termination by lactonization and lactamization, some specially structured alkenes, such as norbomene and related alkenes, can participate in intermolecular carbopalladation-carbonylative ketonization tandem processes. In the reactions shown in Scheme 22, the acylpalladium intermediates undergo intramolecular acylpalladation with arenes to provide ketones. ... 

In conclusion, the intermolecular acylpalladation of alkenes is, so far, limited to specific substrates, and this is mainly due to certain strict requirements, that is, (i) acylpalladation faster than decarbonylation and (ii) a termination step faster than polymeric pathway, and yet slower than acylpalladion itself. Attempts to control this reaction by... 

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