Rhodium-catalyzed Heck-type coupling

Rhodium-catalyzed Heck-type coupling of boronic acids with activated alkenes was carried out in an aqueous emulsion.82 The couplings between arylboronic acids and activated alkenes catalyzed by a water-soluble tm-butyl amphosrhodium complex were found to progress at room temperature to generate Heck-type products with high yields and excellent selectivity. It was necessary to add two equivalents of the... 

Other metals can catalyze Heck-type reactions, although none thus far match the versatility of palladium. Copper salts have been shown to mediate the arylation of olefins, however this reaction most probably differs from the Heck mechanistically. Likewise, complexes of platinum(II), cobalt(I), rhodium(I) and iridium(I) have all been employed in analogous arylation chemistry, although often with disappointing results. Perhaps the most useful alternative is the application of nickel catalysis. Unfortunately, due to the persistence of the nickel(II) hydride complex in the catalytic cycle, the employment of a stoichiometric reductant, such as zinc dust is necessary, however the nickel-catalyzed Heck reaction does offer one distinct advantage. Unlike its palladium counterpart, it is possible to use aliphatic halides. For example, cyclohexyl bromide (108) was coupled to styrene to yield product 110. 

Dubbaka, S.R. and Vogel, P. (2005) Palladium-catalyzed desulfitative Mizoroki-Heck couplings of sulfonyl chlorides with mono- and disubstituted olefins rhodium-catalyzed desulfitative Heck-type reactions under phosphine- and base-free conditions. Chem. Eur. J., 11, 2633-41. 

Ishiyama, T. and Hartwig, J.R (2000) A Heck-type reaction involving carbon-heteroatom double bonds. Rhodium(I)-catalyzed coupling of aryl halides with A-pyrazyl aldimines. J. Am. Chem. Soc., 122, 12043-4. 

Dubbaka, S.R. and Vogel, P. (2005) Palladium-catalyzed desulfltative Mizoroki-Heck coupling of sulfonyl chlorides with mono- and disubstituted olefins rhodium-catalyzed desulfitative Heck-type reactions under phosphine- and base-free conditions. Chem. Eur. J., 11, 2633 1. Kamigata, N., Ozaki, J.-i., and Kobayashi, M. (1985) Reaction of alkenesulfonyl chlorides with olefins catalyzed by a ruthenium(ll) complex. A novel method for synthesis of ( , )- ,4-diaryl-... 

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