State Key Laboratory of Chemical Oncogenomics and Key Laboratory of Chemical Genomics, Shenzhen Engineering Laboratory of Nano Drug Slow-Release, Shenzhen Graduate School of Peking University, Shenzhen 518055, China.
Chem Commun (Camb). 2019 Apr 4;55(29):4206-4209. doi: 10.1039/c9cc00948e.
We have developed a one-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed [3+2] annulation of oxabicyclic alkenes followed by a ring-opening/dehydration sequence in good to excellent yields. With the use of 2-(1-methylhydrazinyl)pyridine (MHP), first explored by our group as the bidentate directing group in C-H functionalization of benzoic hydrazides, the new reaction sequence proceeded smoothly and tolerated a wide range of functional groups, featuring facile scalability. Notably, oxygen served as the green oxidant in the reaction system. Careful tuning of the reaction parameters assured the direct synthesis of benzo[b]fluorenones through aromatization of the dihydroepoxybenzofluorenone intermediate.
我们开发了一种通过钴催化的[3+2]环加成反应，随后进行开环/脱水序列，从氧杂双环烯烃一锅合成苯并[b]荧蒽酮的方法，产率良好至优秀。使用我们小组首次探索的 2-(1-甲基肼基)吡啶（MHP）作为苯甲酰肼 C-H 功能化中的双齿导向基团，新的反应序列顺利进行，并能耐受广泛的官能团，具有易于扩展的特点。值得注意的是，氧气在反应体系中充当绿色氧化剂。通过仔细调整反应参数，可以确保通过二氢环氧苯并荧蒽酮中间体的芳构化直接合成苯并[b]荧蒽酮。
