Aroyl halides reactions with alkenes

Blaser and Spencer used aroyl halides in place of aryl halides, with aroyl chlorides being of specific interest as ubiquitous, relatively cheap compounds ( Blaser reaction ) [24], This latter reaction is normally conducted in aromatic solvents phosphines are not used here as catalyst ligands since they fully inhibit the reaction. In the same way, benzoic acid anhydrides can be used as the aryl source in combination with PdCl2 and catalytic amounts of NaBr [79]. In this reaction, one of the arenes is used in the coupling reaction by elimination of CO, whereas the other benzoate serves as the base. The benzoic acid thus formed can easily be recycled into the anhydride. The use of aryl and vinyl triflates according to Cacchi [25] and Stille [26] extends the scope of the Heck coupling to carbonyl compounds phenol derivatives act via triflate functionalization as synthetic equivalents of the aryl halides. The arylation of cyclic alkenes [27], electron-rich vinyl ethers [28], and allylic alcohols [29] is accessible through Heck reactions. Allylic alcohols yield C-C-saturated carbonyl compounds (aldehydes) for mechanistic reasons (y9-H elimination), as exemplified in eq. (6). 

The acylpalladium halide complex 84 is an intermediate of catalytic decarbony-lation of aroyl halides 83 [53]. The decarbonylation of 84 generates the aryl-palladium intermediate 85 at higher temperature which undergoes facile alkene insertion. Therefore, similar to aryl halides, acyl halides can be used for the alkene insertion. The reaction is carried out with a phosphine-free Pd catalyst in the presence of tertiary amines [54]. Higher yields were obtained by using a mixture of K2CO3 and benzyltrioctylammonium chloride [55]. 

Pd(PhCN)2Cl2 has also been used as an effective precatalyst in the Heck reaction of alkenes with arylsuffonyl chlorides, aroyl chlorides, or aryl halides. Usually, a base was required (eqs 36-38). ... 

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