Synthesis 2016; 48(04): 512-519
DOI: 10.1055/s-0035-1561276
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© Georg Thieme Verlag Stuttgart · New York

Gold(I)-Catalyzed Stereospecific [4+3]-Cycloaddition Reaction of 1-(Alk-1-ynyl)cyclopropyl Ketones with Nitrones: A Modular Entry to Enantioenriched 5,7-Fused Bicyclic Furo[3,4-d][1,2]oxazepines

Yanqing Zhang
a   Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, 3663 N. Zhongshan Road, Shanghai, 200062, P. R. of China   eMail: yjxiao@chem.ecnu.edu.cn
b   Patent Examination Cooperation Jiangsu Center of the Patent Office, Sipo, 88N. Guangqi Road, Suzhou, Jiangsu 215163, P. R. of China
,
Yuanjing Xiao*
a   Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, 3663 N. Zhongshan Road, Shanghai, 200062, P. R. of China   eMail: yjxiao@chem.ecnu.edu.cn
,
Junliang Zhang*
a   Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, 3663 N. Zhongshan Road, Shanghai, 200062, P. R. of China   eMail: yjxiao@chem.ecnu.edu.cn
c   State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, CAS. 345 Lingling Road, Shanghai, 200032, P. R. of China   eMail: jlzhang@chem.ecnu.edu.cn
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Publikationsverlauf

Received: 12. Oktober 2015

Accepted after revision: 06. November 2015

Publikationsdatum:
11. Januar 2016 (online)


Abstract

In our previous study, a gold(I)-catalyzed stereoselective formal [4+3]-cycloaddition reaction of 1-(alk-1-ynyl)cyclopropyl ketones with nitrones was found to afford 5,7-fused bicyclic furo[3,4-d][1,2]oxazepines in good to excellent yields with high diastereoselectivity catalyzed by (triphenylphosphine)gold(I) triflate. In order to gain insight into the mechanism of this [4+3] cycloaddition process, an enantioselective version used a MeO-DTBM-BIPHEP derived gold(I) complex as the catalyst, which resulted in the kinetic resolution of the 1-(alk-1-ynyl)cyclopropyl ketones, affording the recovered ketones in high yield with excellent enantioselectivity. An interesting chirality transfer was observed in the gold(I)-catalyzed [4+3] cycloaddition of optically active 1-(alk-1-ynyl)cyclopropyl ketones with nitrones, indicating the reaction undergoes a stereospecific SN2-type ring-opening of the cyclopropane.

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