钯催化亚烷基环丙基酮开环反应机制的理论研究（英文）  

Density functional methods study on the Pd-catalyzed ring-opening mechanism based on alkylidenecyclopropyl ketones

作　　者：杨筱平[1] 方冉[2] 李志锋[3] 

机构地区：[1]天水师范学院电子与电气工程学院,天水741001 [2]兰州大学化学化工学院功能有机分子化学国家重点实验室,兰州730000 [3]天水师范学院化学工程与技术学院,天水741001

出　　处：《原子与分子物理学报》2016年第6期993-1001,共9页Journal of Atomic and Molecular Physics

基　　金：国家自然科学基金(21463023,21203080)

摘　　要：在BHand HLYP/6-31G(d,p)(Pd用LANL2DZ基组)计算水平上对钯催化的亚烷基环丙酮开环反应机制进行了理论研究,使用极化连续介质模型(PCM)考虑了溶剂(二氯甲烷)的影响.优势路径计算表明,在反应循环的第一步中,Pd通过与羰基O原子及双键配位形成前驱物1a.随后,由于Pd与碳碳双键和羰基氧原子的配位作用提高了碳碳双键的亲电性,从而使得它很容易和相邻的羰基通过[2+2]进行环加成反应.此过程涉及一个从"临界中间体"2a到"临界过渡态"tsa2的"临界转化区域".进一步,C4上的H原子发生迁移形成中间体4a和HPd Cl,HPd Cl进攻C1-C4键生成中间体5a,最后,通过无能垒的过程,生成产物6a,并释放出Pd催化剂R2.The Pd-catalyzed ring-opening mechanism based on alkylidenecyclopropyl ketones have been investigated with density functional theory（DFT） at the BHand HLYP/6-31G（d,p）（LANL2 DZ for Pd） level.Solvent effects on reactions have been explored by calculations that included polarizable continuum model（PCM） for the solvent（dichloromethane）. The calculation results suggest that in the first step of the cycle the preliminary intermediate 1a stabilized by the coordination of the Pd to the carbonyl oxygen atom and the π-bond of the alkenes moiety. Then the coordination of the double bond and the carbonyl oxygen atom with the Pd atom enhances the electrophilicity of the double bond and that further induces a [2 ＋ 2]addition of the carbonyl oxygen onto the double bond. This process involves a ＂critical change region＂from ＂critical intermediate＂2a to＂critical transition state＂tsa2. The subsequent step migration of the hydrogen atoms for C4 leads to the intermediate 4a and HPd Cl. The attack of HPd Cl to C1-C4 bond for the next step would be given intermediate 5a and the finally step results in the formation of the final product 6a without any barrier.

关 键 词：酮 开环反应 钯催化 密度泛函理论 

分 类 号：O41[理学—理论物理]