Heck-Matsuda reaction catalyst

Alternative solvents have been developed for the Heck-Matsuda reaction. This reaction has recently been performed in neat water by Najera s group [95]. The reaction was carried out using an oxime-derived palladacycle catalyst and palladium acetate using a variety of different diazonium tetrafluoroborates giving styrenes, stllbenes, arylideneketones, and cinnamate esters (Figure 1.26). 

The general catalytic cycle for the Heck-Matsuda reaction using acyclic olefins starts with the oxidative addition of the Pd(0) catalyst A to the aryldiazonium salt and sequential elimination of nitrogen to produce the cationic palladium species C. This intermediate is very electrophilic and it promptly... 

These substrate-directed Heck reactions allowed the synthesis of pharmacologically active compounds in a very straightforward way. For example, compotmd 26 was oxidized with DDQ to provide the natural product yango-nine 27. Additionally, methysticin 28 was obtained in 59% yield (95% based on recovered starting material) directly from the Heck-Matsuda reaction. The chemoselective reduction of the least hindered double bond of 28, using Pd/C as catalyst, provided dehydromethysticine 29 in 95% yield (Scheme 11). 

Another particularly attractive substrate class for industrial Heck reactions are the arenediazonium salts, because of to their ready availability from anilines. Matsuda et al. found that for these highly reactive compounds, ligand-free Pd(dba)2 suffices as catalyst [32], Even palladium catalysts on solid supports are highly effective [33], The diazotization of an aniline 25 and its olefination can be performed separately, or in one pot (Scheme 12). 

Nonaqueous IL microemulsions were also used as catalysts to improve reaction efficiency. Gayet et al. established an IL-in-oil microemulsion system with benzylpyridinium bis(trifluoromethanesulfonyl)imide ([BnPyrJNTfj), TX-lOO, and toluene, in which the Matsuda-Heck reaction between methoxybenzene diazotate and 2,3-dihydrofuran took place [46]. The reaction yield in this IL-in-oil microemulsion was twice as high as that in neat ILs. The results provided a basis for designing a nonaqueous IL microemulsion microreactor and also showed that nonaqueous IL microemulsion might have good prospects of applications in biocatalysis and nanomaterial synthesis. 

Fig. 11. Matsuda Heck reaction between p-methoxyphenyl diazonium salt and 2,3-dihydrofurane using a palladium catalyst.

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