以碳硼炔为底物的过渡金属催化偶联环化反应的理论研究

Transition metal-catalyzed cross-coupling cyclization reaction involving carborynes is one of the essential methods to construct functionalized compounds selectively. Carrying out theoretical studies about this kind of reactions can help to figure out many ambiguous issues which could not be accounted for through experimental measures, such as the nature of transition metal-catalysis, and the important role which carboryne group palys in controlling the chemical selectivity of reactions mentioned above. This program aims at conducting theoretical studies about transition metal-catalyzed cross-coupling cyclization reactions involving carborynes, employing density functional theory (DFT) methods such as B3LYP, BHandHLYP, etc. According to optimizing geometrical structures of all possible reactants, intermediates, transition states and products, we can get corresponding structural parameters, absolute energies, relative energies and corresponding potential energy surfaces (PESs), and sequentially disclose the reaction mechanism, solvent effect, substituent effect, as well as the important role which carboryne group palys in controlling the chemical selectivity of transition metal-catalyzed cross-coupling cyclization reactions. The intrinsic reaction coordinates (IRC) will be traced and the connecting relationship between key transition states and the reactants, products will be confirmed. Theory of Atoms in Molecules (AIM) will be employed for topological analysis of electronic density of key stationary points for the sake of obtaining corresponding bonding properties and nature, and then offer some necessary theoretical supports and hints for the experimental preparation of other carboryne compounds, as well as for the development of new reaction systems possesing high and predictable chemical selectivities.

以碳硼炔为底物的过渡金属催化偶联环化反应是选择性地构筑功能化合物的重要方法之一，对其开展理论研究有助于深入认识过渡金属催化的本质以及碳硼炔在控制此类反应的化学选择性方面所起的关键作用。申请项目旨在采用密度泛函的B3LYP、BHandHLYP等方法对碳硼炔参与的过渡金属催化偶联环化反应进行理论研究。通过优化反应途径上所有可能的反应物、中间体、过渡态和产物的几何构型，得到其结构参数、绝对能量、相对能量以及对应的势能剖面图，揭示过渡金属催化偶联环化反应的微观反应机制，从理论层面探究与确证碳硼炔基团在控制该反应的化学选择性方面所扮演的重要角色，并重点讨论溶剂效应和取代基效应。对反应路径上的关键过渡态使用内禀反应坐标（IRC）加以分析确认，对关键驻点使用AIM理论进行电子密度拓扑分析，以获得其成键性质，为制备其他碳硼炔化合物以及开发具有高选择性和可预见选择性的新反应系统提供必要的理论支持与指引。

过渡金属催化碳硼烷或碳硼炔与不饱和化合物的环加成反应在选择性构筑功能碳硼烷衍生物方面有重要应用。实验上已经成功制备得到了一系列结构新颖、性质独特的环状碳硼烷衍生物，但相应的微观机理、反应选择性控制因素、取代基作用机制等尚不明确。本项目运用密度泛函理论的B3LYP、X3LYP、CAM-B3LYP、ωB97xD、M06-2X等方法对NiCl2(PPh3)2催化碳硼炔与炔烃的[2+2+2]三组分环化反应、NiCl2(PPh3)2催化碳硼炔与炔烃和烯烃的[2+2+2]三组分环化反应、Zr/Ni共催化碳硼炔与烯烃和炔烃的[2+2+1]三组分环化反应、以及碳硼炔与环戊二烯衍生物的[4+2]环化反应、CpRuCl(PPh3)2-MeI共催化降冰片二烯与炔烃的[3+2]/[2+2]环化反应等开展了理论研究。通过优化反应途径上所有可能的反应物、中间体、过渡态和产物的几何构型，获得了各反应路径上所有驻点的几何结构参数、绝对能量、相对能量以及对应的势能剖面图，从而确定了目标反应的微观机理、最优反应路径和决速步。对于被研究的每一类反应，都从理论化学层面对实验中所观测到的取代基效应、化学选择性、区域选择性、以及碳硼烷基和催化剂所扮演的角色等给出了合理的理论解释。该研究成果对于人们深入认识过渡金属催化的本质以及碳硼烷基在控制此类反应的化学、区域选择性方面所起的作用具有一定意义，对于开发具有高选择性和可预见选择性的新反应系统、制备更多官能化碳硼烷衍生物也有一定的参考价值。