Controlling remote selectivity and delivering novel functionalities at distal positions in arenes are an important endeavor in contemporary organic synthesis. In this vein, template engineering and mechanistic understanding of new functionalization strategies are essential for enhancing the scope of such methods. Herein, meta-C-H allylation of arenes has been achieved with the aid of palladium catalyst, pyrimidine-based auxiliary and allyl phosphate. 1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) was found as a critical solvent in this transformation. The role of HFIP throughout catalytic cycle has been systematically studied. A broad substrate scope with phenethyl ether, phenol, benzylsulfonyl ester, phenethylsulfonyl ester, phenylacetic acid, hydrocinnamic acid and 2-phenylbenzoic acid derivatives have been demonstrated. Interestingly, conformation-ally flexible arenes have also been selectively allylated at meta-position using allyl phosphate. A combination of 1H NMR, 31P NMR, ESI-MS, kinetic experiments, and density functional theory (DFT) computations suggested that reaction proceeds through a ligand-assisted meta-C-H activation, allyl addition forming a Pd-π-allyl complex which is then followed by a turn-over determining C-C bond formation step leading to the meta-allylated product.

中文翻译：

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钯催化的芳烃间位 C-H 烯丙基化：基于嘧啶的模板和六氟异丙醇的独特组合

控制远程选择性并在芳烃的远端位置提供新功能是当代有机合成中的一项重要努力。在这方面，模板工程和对新功能化策略的机械理解对于扩大此类方法的范围至关重要。在此，在钯催化剂、嘧啶类助剂和磷酸烯丙酯的帮助下，实现了芳烃的间位CH烯丙基化。发现 1,1,1,3,3,3-六氟异丙醇 (HFIP) 是该转化过程中的关键溶剂。已经系统地研究了 HFIP 在整个催化循环中的作用。苯乙醚、苯酚、苄基磺酰基酯、苯乙基磺酰基酯、苯乙酸、氢化肉桂酸和 2-苯基苯甲酸衍生物的广泛底物范围已被证明。有趣的是，构象灵活的芳烃也已使用磷酸烯丙酯在间位选择性地烯丙基化。1H NMR、31P NMR、ESI-MS、动力学实验和密度泛函理论 (DFT) 计算的组合表明，反应通过配体辅助的间位 CH 活化进行，烯丙基加成形成 Pd-π-烯丙基复合物然后是翻转确定 CC 键形成步骤，导致间位烯丙基化产物。