One-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed MHP-directed [3+2] annulation/ring-opening/dehydration sequence

Shuxian Qiu; Shengxian Zhai; Huifei Wang; Xiaoming Chen; Hongbin Zhai

doi:10.1039/C9CC00948E

One-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed MHP-directed [3+2] annulation/ring-opening/dehydration sequence†

Shuxian Qiu,^a Shengxian Zhai,^b Huifei Wang,^c Xiaoming Chen^a and Hongbin Zhai

*^ade

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* Corresponding authors

^a 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
E-mail: zhaihb@pku.edu.cn

^b College of Chemistry & Environmental Engineering, Anyang Institute of Technology, Anyang 455000, China

^c School of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China

^d State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China

^e Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300071, China

Abstract

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.

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DOI: https://doi.org/10.1039/C9CC00948E
Article type: Communication
Submitted: 01 Feb 2019
Accepted: 13 Mar 2019
First published: 14 Mar 2019

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Chem. Commun., 2019,55, 4206-4209

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One-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed MHP-directed [3+2] annulation/ring-opening/dehydration sequence

S. Qiu, S. Zhai, H. Wang, X. Chen and H. Zhai, Chem. Commun., 2019, 55, 4206 DOI: 10.1039/C9CC00948E

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Chemical Communications

One-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed MHP-directed [3+2] annulation/ring-opening/dehydration sequence†

Abstract

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One-pot synthesis of benzo[b]fluorenones via a cobalt-catalyzed MHP-directed [3+2] annulation/ring-opening/dehydration sequence

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