Copper(II)-Mediated Ring Opening/Alkynylation of Tertiary Cyclopropanols by Using Nonmodified Terminal Alkynes
Bu-Qing Cheng, Si-Xuan Zhang, Yan-Ying Cui, Xue-Qiang Chu, Weidong Rao, Haiyan Xu, Guo-Zhi Han* and Zhi-Liang Shen*
*Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Nanjing Tech
University, Nanjing 211816, China, Email: han
njtech.edu.cn,
ias_zlshennjtech.edu.cn
B.-Q. Cheng, S.-X. Zhang, Y.-Y. Cui, X.-Q. Chu, W. Rao, H. Xu, G.-Z. Han, Z.-L. Shen, Org. Lett., 2020, 22, 5456-5461.
DOI: 10.1021/acs.orglett.0c01828
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Abstract
Copper(II)-mediated ring opening/alkynylation of cyclopropanols with inexpensive and commercially available terminal alkynes proceeded efficiently to afford synthetically useful alk-4-yn-1-ones in good yields with good functional group tolerance.
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proposed mechanism
Details
The document discusses a study on the copper(II)-mediated ring opening and alkynylation of tertiary cyclopropanols using nonmodified terminal alkynes. This method is efficient and employs inexpensive, commercially available terminal alkynes to produce alk-4-yn-1-ones, which are valuable intermediates in organic synthesis. The reactions proceed with good functional group tolerance and yield moderate to good results. The study highlights the optimization of reaction conditions, including the use of Cu(OAc)2 as the optimal mediator and N-methylpyrrolidone (NMP) as the best solvent. Various metal salts and solvents were tested, but Cu(OAc)2 in NMP provided the highest yields. The substrate scope was explored, showing that both electron-withdrawing and electron-donating substituents on the phenyl ring of alkynes, as well as different cyclopropanols, worked well under the optimized conditions. Control experiments suggested that the reaction mechanism involves the formation of copper homoenolate and/or alkynylcopper species. The study concludes that this method is practical and straightforward for synthesizing alk-4-yn-1-ones, even with inexpensive terminal alkynes, without needing preprepared reactive alkynes. The findings are significant for advancing the synthesis of versatile organic compounds.
Key Words
ID: J54-Y2020
