State Key Laboratory of Chemical Resource Engineering & Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China.
J Am Chem Soc. 2020 May 13;142(19):9017-9027. doi: 10.1021/jacs.0c02997. Epub 2020 May 1.
C-N formation is of great significance to synthetic chemistry, as N-containing products are widely used in chemistry, medicine, and biology. Addition of an amine to an unsaturated carbon-carbon bond is a simple yet effective route to produce new C-N bonds. But how to effectively conduct an anti-Markovnikov addition with high selectivity has been a great challenge. Here, we proposed a strategy for highly regioselective C-N addition via hydroamination by using supported Pt. It has been identified that atomic-scale Pt is the active site for C-N addition with Pt for Markovnikov C-N formation and atomic Pt (Pt and Pt) contributing to anti-Markovnikov C-N formation. A selectivity of up to 92% to the anti-Markovnikov product has been achieved with atomic Pt in the addition of styrene and pyrrolidine. A cooperating catalysis for the anti-Markovnikov C-N formation between Pt and Pt has been revealed. The reaction mechanism has been studied by EPR spectra and in situ FT-IR spectra of adsorption/desorption of styrene and/or pyrrolidine. It has been demonstrated that Pt activates amine to be electrophilic, while Pt activates C═C by π-bonding to make β-C nucleophilic. The attack of nucleophilic β-C to electrophilic amine affords the anti-Markovnikov addition. This strategy proves highly effective to a variety of substrates in anti-Markovnikov C-N formation, including aromatic/aliphatic amines reacting with aromatic olefins, aromatic/aliphatic olefins with aromatic amines, and linear aliphatic olefins with secondary aliphatic amines. It is believed that the results provide evidence for the function of varied chemical states in monatomic catalysis.
C-N 键的形成对于合成化学具有重要意义，因为含氮产物广泛应用于化学、医学和生物学领域。在不饱和碳-碳键上加成胺是生成新 C-N 键的简单而有效的方法。但是，如何有效地以高选择性进行反马氏加成一直是一个巨大的挑战。在这里，我们提出了一种通过负载型 Pt 进行氨氢化高区域选择性 C-N 加成的策略。已经确定原子级 Pt 是 C-N 加成的活性位，Pt 用于马氏 C-N 形成，而原子 Pt（Pt 和 Pt）有助于反马氏 C-N 形成。在苯乙烯和吡咯烷的加成中，原子 Pt 实现了高达 92%的反马氏加成产物的选择性。揭示了 Pt 和 Pt 之间协同催化反马氏 C-N 形成。通过 EPR 光谱和苯乙烯和/或吡咯烷的吸附/解吸的原位 FT-IR 光谱研究了反应机理。结果表明，Pt 使胺活化成亲电试剂，而 Pt 通过π键合使 C═C 活化，从而使β-C 亲核化。亲核β-C 对亲电胺的进攻得到反马氏加成产物。该策略在反马氏 C-N 形成中对多种底物具有高效性，包括芳基/脂肪族胺与芳基烯烃、芳基/脂肪族烯烃与芳族胺以及线性脂肪族烯烃与仲脂肪族胺的反应。这一结果为单原子催化中多种化学状态的功能提供了证据。
