Molybdenum-Catalyzed Enantioselective Sulfoxidation Controlled by a Nonclassical Hydrogen Bond between Coordinated Chiral Imidazolium-Based Dicarboxylate and Peroxido Ligands
作者:Carlos Carrasco、Francisco Montilla、Agustín Galindo
DOI:10.3390/molecules23071595
日期:——
Chiral alkyl aryl sulfoxides were obtained by molybdenum-catalyzed oxidation of alkyl aryl sulfides with hydrogen peroxide as oxidant in mild conditions with high yields and moderate enantioselectivities. The asymmetry is generated by the use of imidazolium-based dicarboxylic compounds, HLR. The in-situ-generated catalyst, a mixture of aqueous [Mo(O)(O2)2(H2O)n] with HLR as chirality inductors, in
手性烷基芳基亚砜是通过钼催化氧化烷基芳基硫化物与过氧化氢作为氧化剂在温和条件下以高产率和中等对映选择性获得的。不对称性是通过使用基于咪唑鎓的二羧酸化合物 HLR 产生的。原位生成的催化剂,[Mo(O)(O2)2(H2O)n] 水溶液与 HLR 作为手性诱导剂的混合物,在 [PPh4]Br 存在下,被鉴定为阴离子双核络合物 [PPh4 ][Mo(O)(O2)2(H2O)]2(μ-LR)},根据光谱数据和密度泛函理论 (DFT) 计算。配位 (LR)- 的烷基 R 基团的一个 C-H 键与过氧化物配体的一个氧原子之间的非经典氢键被确定为导致该过程不对称的相互作用。此外,通过定位模型复合物 [Mo(O)(O2)2(H2O)(κ1-O-LR)]− (R = H, iPr)。∆∆G≠ 约为。0 kcal∙mol−1 对于 R = H,外消旋亚砜,同时对于手性物质,ΔΔG≠ 为 ca。2 kcal∙mol−1