Aryl Carbamates: Mechanisms of Orthosodiations and Snieckus-Fries Rearrangements
Aryl Carbamates: Mechanisms of Orthosodiations and Snieckus-Fries Rearrangements
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DOI：
10.1021/acs.joc.9b00968
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发表时间：
2019-07-19
影响因子：
3.6
通讯作者：
Collum, David B.
中科院分区：
文献类型：
--
作者：
Ma, Yun;Woltornist, Ryan A.;Collum, David B.
芳基氨基甲酸酯在四氢呋喃中被二异丙基氨基钠（NaDA）邻位取代。得到的芳基钠进行Snieckus Fries重排，以良好的产率得到邻酰化苯酚。中间体芳基钠和所得的邻酰化苯酚酯被认为是单体的。两步反应中的限速步骤取决于芳烃间位取代基和氨基甲酰基的Meta位阻要求。率的研究揭示了一个占主导地位的溶解单体为基础的orthopolization其次是二或三溶剂化芳基钠单体为基础的重排。NaDA催化的Snieckus Fries重排的动力学证据表明混合三聚体的中间性。竞争性卤化物消除形成苯炔进行了讨论。
Aryl carbamates are orthometalated by sodium diisopropylamide (NaDA) in tetrahydrofuran. The resulting arylsodiums undergo Snieckus Fries rearrangement to give orthoacylated phenols in good yield. The intermediate arylsodiums and resulting orthoacylated phenolates are suggested to be monomeric. The rate-limiting step in the two-step sequence depends on the steric demands of the carbamoyl moiety and the substituents in the meta position of the arene. Rate studies reveal a dominant disolvated-monomer-based orthometalation followed by a di- or trisolvated arylsodium monomer-based rearrangement. Kinetic evidence of a NaDA-catalyzed Snieckus Fries rearrangement suggests the intermediacy of mixed trimers. Competitive halide eliminations to form benzyne are also discussed.