Mechanism of palladium-catalyzed decarboxylative cross-coupling between cyanoacetate salts and aryl halides

作者：Jiang YuanYe; Fu Yao^*; Liu Lei

来源：Science China Chemistry, 2012, 55(10): 2057-2062.

DOI：10.1007/s11426-012-4672-0

• palladium
• catalytic
• decarboxylation
• mechanism
• density functional theory

Recently we reported Pd-catalyzed decarboxylative cross-coupling of cyanoacetate salts with aryl halides and triflates. This reaction shows good functional group tolerance and is useful for the synthesis of alpha-aryl nitriles. To elucidate the mechanism for this reaction, we now carry out a density functional theory study on the cross-coupling of potassium cyanoacetate with bromobenzene. Our results show that the decarboxylation transition state involving the interaction of Pd with the alpha-carbon atom has a very high energy barrier of +34.5 kcal/mol and therefore, must be excluded. Decarboxylation of free ion (or tight-ion-pair) also causes a high energy increase and should be ruled out. Thus the most favored decarboxylation mechanism corresponds to a transition state in which Pd interacts with the cyano nitrogen. The energy profile of the whole catalytic cycle shows that decarboxylation is the rate-determining step. The total energy barrier is +27.5 kcal/mol, which is comprised of two parts, i.e. the energy barrier for decarboxylation and the energy cost for transmetallation.

• 出版日期2012-10
• 单位清华大学