铑(Ⅰ)催化烯烃碳酰化反应机理:手性聚稠环过程的对映选择性  

Reaction Mechanism of Rh(Ⅰ)-catalyzed Olefin Carboacylation:Enantioselectivity in the Formation of Chiral Poly-fused Rings

作　　者：程学礼[1] 李衍飞[1] 赵燕云[1] 刘永军[2] 

机构地区：[1]泰山学院化学化工学院,泰安271000 [2]山东大学化学化工学院,济南250100

出　　处：《高等学校化学学报》2018年第3期521-529,共9页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:21502136;21571137;51702228);山东省自然科学基金(批准号:ZR2017LB010);泰山学院引进人才科研启动基金(批准号:Y-01-2013010)资助~~

摘　　要：采用密度泛函理论方法研究了[Rh(R,R-DIOP)]+[DIOP=(1R,2R)-1,2-O-异丙叉-1,2-二醚氧基-1,2-双(二苯基磷基)乙烷]催化下苯并环丁酮手性聚稠环过程在气相、四氢乙呋喃(THF)及水中的反应机理.计算结果表明,在气相中反应容易进行,经TS2形成六元环的过程为决速步骤,但产物无明显的对映选择性.在THF中,S-和R-通道的C—C键活化能垒仅由79.5和69.3 kJ/mol提高到80.2和88.8 kJ/mol,未改变反应的实质;Rh与2个C原子的配位明显弱于气相,相对于催化剂和反应物自由能之和,S-和R-通道的反应总能垒分别提高到63.8和68.1 kJ/mol.对于S-通道,溶剂THF使经TS2的能垒升至112.0 kJ/mol,仍为整个过程的决速步骤;然而对R-通道,溶剂使经TS1形成五元环过程的能垒升至91.5 kJ/mol,但使经TS2的能垒由78.9 kJ/mol降至77.7 kJ/mol,IM1→TS1成为决速步骤.在以水为溶剂时,经TS1形成五元环的过程成为2个通道的决速步骤,其在S-和R-通道中的能垒分别为102.5和94.9 kJ/mol.因此,溶剂改变了反应的决速步骤及能垒.3种方法均预测R-通道为主反应路径,但THF能明显增加产物的对映选择性.采用自然键轨道(NBO)电荷分析了反应过程中电荷的变化.Density functional theory（DFT） methods were employed to investigate the reaction mechanisms of the formation of chiral poly-fused rings of benzocyclobutenone catalyzed by [Rh（R,R-DIOP） ]＋in gas phase,THF and water.The theoretical results show that,the reaction system will proceed easily in gas phase,and the formation of the six-membered rings via TS2 is the rate-determining step,but the products are no distinct enantioselectivity.For the S-and R-channels in THF,the free energy barriers of C—C activation are elevated slightly from 79.5 and 69.3 kJ/mol to 80.2 and 88.8 kJ/mol,respectively,but do not alter the reaction characters.The coordination of Rh with the two C atoms is much weaker than that in gas phase,and the total free-energy barriers relative to the catalyst and the reactant in the S-and R-pathways are increased to 63.8 and68.1 kJ/mol.For the S-channel,THF as solvent markedly increases the barrier via TS2 to 112.0 kJ/mol,and the process is still the rate-determining step.However,to the R-pathway,THF increases the barrier of forming the five-membered ring to 91.5 kJ/mol,but decreases the barrier via TS2 from 78.9 kJ/mol to 77.7 kJ/mol,so IM1→TS1 becomes the rate-determining step.When employing water as the solvent,the formation of the five-membered rings via TS1 becomes the rate-determining steps of these two reaction pathways,and the barriers of the S-and R-channels are 102.5 and 94.9 kJ/mol.As a result,solvents alter the rate-determining steps and their energy barriers of the reaction system.All these 3 methods predict that the R-pathway is the predominated reaction channel,but THF can evidently increase the enantioselectivity.The charge population was also analyzed by using the natural bond orbital（NBO） charges.

关 键 词：烯烃碳酰化 [Rh(R R-DIOP)]+ 对映选择性 手性聚稠环 

分 类 号：O641.1[理学—物理化学] O643.3[理学—化学]