Abstract
Ni(acac)2/N-heterocyclic carbene-derived catalysts were shown to be highly efficient in the nickel-catalyzed Heck reaction. Various aryl halides were reacted with acrylate to give the coupled products in good to high yield.
Key words
nickel - carbene ligands - Heck reaction - catalysis
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11b Reactions in toluene, dioxane, NMP, and DMA proceeded in relatively poor yields.
12 Use of Ag2CO3, t-BuOK, CsF, CsOAc, or Et3N rather than Cs2CO3, K2CO3 or Na2CO3, led to a decreased yield. In addition, after the catalyst optimization (Table 1), it was found that the use of Na2CO3 gave similar but slightly better results than Cs2CO3 in almost all cases (Table 2).
13 Reactions of aryl bromides in the absence of Bu4NI resulted in poorer yields. However, the role of such an ammonium salt is obscure at present.
14 Under the optimized conditions we developed here, we have not yet obtained the products in satisfactory yields from the reaction of aryl chlorides.
