Heck reaction acyl halides

An unusual synthesis of acyldienes from conjugated dienes, carbon monoxide, and alkyl or acyl halides using cobalt carbonylate anion as a catalyst should be mentioned here (57). The reaction apparently involves the addition of an acylcobalt carbonyl to a conjugated diene to produce a l-acylmethyl-7r-allylcobalt tricarbonyl, followed by elimination of cobalt hydrocarbonyl in the presence of base. The reaction can thus be made catalytic. Since the reaction was discussed in detail in the recent review by Heck (59), it will not be pursued further here. 

As briefly indicated in the Introduction (see p. 64), alkyl and acyl halides have been converted into cobalt derivatives by replacing the halide ion with cobalt tetracarbonyl anion. The cobalt derivatives were also cleaved by methanol, resulting in compounds in which carbon monoxide had been inserted. Although application of Heck s procedure to the glycosyl halides failed, use of the modification described next enabled the reactions to be carried out successfully. 

It would be more interesting and useful if the reaction could be made catalytic. Actually, catalytic decarbonylation reaction was found to be possible by using chlorocarbonylbis(triphenylphosphine) rhodium (XII) (26). This complex is reasonably stable, and more importantly it is four-coordinated and coordinatedly unsaturated, so that it may expand to a six-coordinated complex by the oxidative addition of acyl halides or aldehydes. The oxidative addition of methyl iodide to similar complexes was reported by Heck (5). 

Shortly thereafter, a more general palladium-catalyzed carbonylative Heck reaction of aryl halides was able to be developed by our group [34]. For the first time, various aromatic and aliphatic alkenes were used successfully in this system, and good yields of the corresponding a,jS-unsaturated ketones were obtained (41-90 %). Starting from easily available aryl iodides and bromides, interesting building blocks were obtained under mild conditions (Scheme 7.15). With respect to the reaction mechanism, the aryl palladium complex and acyl palladium complex were characterized by X-ray, and the mechanism was studied step by step. The results fit well with DFT calculations. 

Cross Coupling. In cross-coupling reactions, an aryl, vinyl, or acyl halide or triflate undergoes a palladium-catalyzed Heck-type coupling to an aryl-, vinyl-, or alkyl-metal reagent (eq 14) to give a new carbon-carbon bond. ... 

This type of reaction, which has been the subject of many studies because of its potential utilization in the decarbonylation of acyl halides, has also been investigated with the analogous iridium(I) complex. The reversibility of the carbonylation/decarbonylation process was first described by Heck and Breslow in 1960, 5 and work with a wide range of organic substrates has been... 

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