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Enantioselective Reductive Divinylation of Unactivated Alkenes by Nickel-Catalyzed Cyclization Coupling Reaction

Jin-Bao Qiao, Ya-Qian Zhang, Qi-Wei Yao, Zhen-Zhen Zhao, Xuejing Peng and Xing-Zhong Shu*

*State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, 222 South Tianshui Road, Lanzhou 730000, China, Email: shuxingzhlzu.edu.cn

J.-B. Qiao, Y.-Q. Zhang, Q.-W. Yao, Z.-Z. Zhao, X. Peng, X.-Z. Shu, J. Am. Chem. Soc., 2021, 143, 12961-12967.

DOI: 10.1021/jacs.1c05670


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Abstract

An enantioselective cross-electrophile divinylation reaction of 2-bromo-1,6-dienes offers a mild route to chiral cyclic architectures, which are key structural motifs found in various biologically active compounds. The use of chiral t-Bu-pmrox and 3,5-difluoro-pyrox ligands resulted in the formation of divinylated products with high chemo-, regio-, and enantioselectivity.

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proposed mechanism



Ni-catalyzed enantioselective cyclization-coupling reactions

General Procedure A: The procedure was conducted in an argon-filled glove box. To a reaction tube equipped with a magnetic stir bar was charged with NiBr2 (4.4 mg, 0.02 mmol), chiral t-Bu-pmrox (8.2 mg, 0.04 mmol), Zn (39.2 mg, 0.6 mmol), and DMA (1.0 mL). After letting the reaction mixture stand for two minutes, the clean solution turned to be black turbid. A solution of tethered diene 1 (0.2 mmol) and vinyl electrophiles 2 (0.3 mmol) in DMF (1.0 mL) was added. The reaction tube was sealed and removed from the glove box. These operations were performed at room temperature and usually took 5-7 min from the addition of 1 and 2. The reaction mixture was then cooled down to -5 C and stirred for 24 h. The reaction mixture was diluted with ethyl acetate (20 mL), washed with water (10 mL) and brine (10 mL), dried over anhydrous Na2SO4, and concentrated in vacuum. The residue was purified by flash chromatography on silica gel (PE/EA = 20:1, 10:1, or 5:1) to afford the desired products.


Key Words

pyrrolidines, Zinc


ID: J48-Y2021