Highly Efficient Nickel-Catalyzed Heck Reaction Using Ni(acac)₂/N-Heterocyclic Carbene Catalyst

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

References

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• 11a

  Other nickel sources such as NiCl₂ and Ni(OAc)₂ were ineffective.

• 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.