State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences , Lanzhou 730000, P. R. China.
State Key Laboratory of Applied Organic Chemistry, Lanzhou University , Lanzhou 730000, P. R. China.
J Org Chem. 2017 Jul 7;82(13):6922-6931. doi: 10.1021/acs.joc.7b01119. Epub 2017 Jun 14.
In the presence of manganese oxide octahedral molecular sieve (OMS-2) supported copper hydroxide Cu(OH)/OMS-2, aerobic synthesis of benzoxazoles from catechols and amines via domino oxidation/cyclization at room temperature is achieved. This heterogeneous benzoxazoles synthesis initiated by the efficient oxidation of catechols over Cu(OH)/OMS-2 tolerates a variety of substrates, especially amines containing sensitive groups (hydroxyl, cyano, amino, vinyl, ethynyl, ester, and even acetyl groups) and heterocycles, which affords functionalized benzoxazoles in good to excellent yields by employing low catalyst loading (2 mol % Cu). The characterization and plausible catalytic mechanism of Cu(OH)/OMS-2 are described. The notable features of our catalytic protocol such as the use of air as the benign oxidant and EtOH as the solvent, mild conditions, ease of product separation, being scalable up to the gram level, and superior reusability of catalyst (up to 10 cycles) make it more practical and environmentally friendly for organic synthesis.
在锰氧化物八面体分子筛（OMS-2）负载的氢氧化铜 Cu(OH)/OMS-2 的存在下，通过邻苯二酚和胺的级联氧化/环化反应，在室温下实现了苯并恶唑的有氧合成。这种非均相苯并恶唑合成是由 Cu(OH)/OMS-2 对邻苯二酚的有效氧化引发的，它可以容忍多种底物，特别是含有敏感基团（羟基、氰基、氨基、乙烯基、乙炔基、酯基，甚至乙酰基）的胺和杂环，通过使用低催化剂负载量（2 mol% Cu），可以得到官能化的苯并恶唑，产率良好至优秀。描述了 Cu(OH)/OMS-2 的表征和合理的催化机理。我们的催化方案的显著特点，如使用空气作为良性氧化剂和 EtOH 作为溶剂、温和的条件、易于产物分离、可扩展至克级水平以及催化剂的高重复使用性（高达 10 个循环），使其更适合于有机合成，具有更好的实用性和环境友好性。
