【作者】 张永强；

【导师】 金云鹤；

【作者基本信息】 大连理工大学 ， 无机化学， 2025， 博士

【摘要】 C-H键活化作为合成化学中快速发展的研究方向之一,一直吸引着广大科研工作者的关注。其中,烷烃来源广泛、储量庞大,是一种理想的sp³碳源。通过烷烃C（sp³）-H键直接活化及官能团化,则可将其高效简捷地转化为高附加值化学品。然而,烷烃分子自身固有的惰性、较高的键解离能（BDE）、较低的键极性以及在功能化过程中难以调控的选择性,均使其C-H键的直接活化过程具有较大的挑战性。因此前期对烷烃功能化反应研究往往需要底物预活化,且反应条件相对苛刻,消耗额外能源的同时降低了原子利用率。光诱导自由基介导的氢原子转移（HAT）作为活化烷烃C（sp³）-H键的一种经典可靠的策略,其过程的高效性结合光反应的条件温和性与绿色环保性赋予了该方式良好的应用前景。本论文中,我们基于光促HAT策略活化烷烃为烷基自由基,分别利用自由基捕获—串联环化、对炔烃的立体选择性自由基加成、限域效应调控的双自由基偶联等方式对烷烃C（sp³）-H键芳基化与烯基化反应开展了系统研究。反应方法的成功开发不仅为完善可持续化学工艺提供了可能,也为发展新型催化剂和反应体系开辟了新路径。首先,利用光激发单电子还原H₂O₂生成的羟基自由基作为HAT试剂活化烷烃C（sp³）–H键,通过异腈类捕获剂对烷基自由基的捕获以及分子内级联环化过程,成功实现无金属参与的多种烷烃的菲啶化过程。该方法使用2,4,5,6-四（九氢-咔唑基）间苯二腈（4-Cz IPN）作为光敏剂,H₂O₂作为HAT试剂羟基自由基前体,联苯基异腈作为芳基化试剂,在可见光照射的温和条件下高收率、高区域选择性地合成包括天然产物trisphaeridine在内的一系列烷基化菲啶类衍生物。第二,利用铁-氯配合物光诱导配体-金属电荷转移（LMCT）过程产生的氯自由基作为HAT试剂活化烷烃C（sp³）–H键,利用烷基自由基对炔烃的选择性加成以及串联的自由基介导构型翻转,成功搭建立体选择性的烷烃烯基化反应平台。该方法利用大位阻联萘酚作为配体,在单一铁催化循环中同时实现烷烃C（sp³）–H活化和烯基化过程立体选择性调控,以高效合成热力学不利的顺式烯烃,反应条件温和,底物适用性广泛,能够耐受多种结构复杂的天然产物及药物分子。通过串联反应,以多异丙基取代二苯二硫醚作为催化剂,能够在可见光照射下高立体选择性实现顺式到反式烯烃的异构化过程,并有效抑制该过程中的双键迁移行为。最后,基于金属有机框架（MOF）材料限域空间电子转移策略,通过光诱导铜-氯金属节点LMCT过程产生氯自由基作为HAT试剂,对烷烃C（sp³）–H键进行活化,通过光激发桥联配体单电子转移（SET）过程激活官能化试剂产生官能化自由基,依托空间及动力学限域效应促进双自由基交叉偶联,实现烷烃C（sp³）-H芳基化过程。该方法利用有机光敏剂三苯基吡喃盐模拟物PYTC⁺作为有机桥联配体,具有光氧化还原活性的铜离子作为金属节点,构筑一例高度有序的多孔结晶MOF材料Cu-PYTC⁺,并将其作为非均相光氧化还原催化剂,利用连续光激发过程,有效实现了烷烃与多氟芳烃间具有挑战性的双自由基偶联过程。该体系展现出了优异的催化性能、良好的底物适用性和区域选择性。更多还原

【Abstract】 As one of the rapidly developed research orientations in synthetic chemistry,C-H bond activation has attracted much science researchers’attention.Thereinto,alkanes are a kind of ideal sp³-carbon source with an extensive source and enormous reserves.Alkanes can be transformed into high-valued chemicals efficiently via direct C（sp³）-H bond activation and functionalization.However,the inherent inertness,high bond dissociation energy（BDE）,low bond polarity of alkanes and the uncontrollable selectivity in the functionalization processes lead to a great challenge for achieving direct C-H bonds activation.In previous studies,pre-activation of alkanes under hash reaction conditions is always required for C-H bond functionalization,not only consuming extra energy but also reducing atom utilization.Photoinduced radical-mediated hydrogen atom transfer（HAT）is a classical and reliable strategy for the activation of alkane C（sp³）–H bonds.Merging the high efficiency of HAT with the mild conditions and environmental friendliness of photoreactions endows this method with great application prospects.In this dissertation,we took advantage of the photo-driven radical-mediated HAT strategy as a basic means to activate alkanes and transform them into alkyl radicals.Systematic research for alkane C（sp³）–H arylation and alkenylation were respectively carried out via radical capture-cascade intramolecular cyclization,stereoselective radical addition to the alkyne,and confined effect-mediated radical-radical coupling.Successful development of these methods not only provided the possibility for improving sustainable chemical technology,but also paved new ways for developing novel catalysts and reaction systems.Firstly,the alkane C（sp³）–H bond was activated by a hydroxyl radical generated by photoexcited single electron reduction of H₂O₂ as a HAT agent.Metal-free phenanthridinylation of various alkanes was realized successfully via alkyl radical capturing by isocyanides and cascade intramolecular cyclization.The method used 2,4,5,6-tetra（9H-carbazol-9-yl）isophthalonitrile（4-Cz IPN）as a photocatalyst,H₂O₂ as the hydroxyl radical precursor,and 2-phenyl isocyanide as an arylation agent.A series of alkylated phenanthridine derivatives containing the natural product trisphaeridine were synthesized with high yields and regioselectivity under mild conditions.Secondly,the alkane C（sp³）–H bond was activated by a chlorine radical generated by the photoinduced ligand-to-metal charge transfer（LMCT）process of an iron-chlorine complex as a HAT agent.A stereoselective alkane alkenylation platform was constructed via selective addition between alkyl radicals and alkynes and cascade radical-mediated configuration flipping.Binaphthol with a large steric hindrance was used as a ligand in this method.Alkane C（sp³）–H activation and stereoselectivity-regulation of alkenylation were realized simultaneously in a onefold iron catalytic cycle to synthesize thermodynamic-unfavored Z-alkene.The system exhibited mild reaction conditions,extensive substrate applicability,and good tolerance for numerous natural products and drug molecules with complex structures.Z-E isomerization of alkene under visible light irradiation was also achieved with high E-stereoselectivity using a catalytic amount of multi-isopropyl-substituted diphenyl disulfide via a tandem reaction.Double-bond migration manner was effectively suppressed with this catalyst.Finally,based on the confined electron transfer strategy inside the metal-organic framework（MOF）system,the alkane C（sp³）–H bond was activated by a chlorine radical generated by the photoinduced LMCT process of copper-chlorine nodes as a HAT agent,and the functionalizing radical was provided via activating the functionalizing agent by single electron transfer（SET）with the photoexcited bridging ligand.Taking advantage of the spatially and kinetically confined effects of this material,the alkane C（sp³）-H alkylation via radical-radical cross-coupling in confined space was realized.In this method,a highly ordered porous crystalline MOF material Cu-PYTC⁺was established by using photosensitizer 2,4,6-triphenylpyrylium mimic PYTC⁺as the organic bridging ligands and photoredox copper ions as the metal nodes.As a heterogeneous photoredox catalyst,the established MOF could realize a challenge radical-radical coupling between alkanes and multifluoroarenes via successive photoexcitation processes with excellent catalytic efficiency and good substrate suitability and stereoselectivity.更多还原