Cyclization of 2-Ethynylphenyl Vinyl Ether Catalyzed by a Ruthenium Complex: Mechanism of Catalytic Cyclization and Stoichiometric Cycloisomerization

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• 作者：Chi-Ren Chen ; Ying-Xuan Lai ; Rong-Yu Wu ; Yi-Hung Liu and Prof. Dr. Ying-Chih Lin
• 刊名：ChemCatChem
• 出版年：2016
• 出版时间：July 6, 2016
• 年：2016
• 卷：8
• 期：13
• 页码：2193-2196
• 全文大小：720K
• ISSN：1867-3899

文摘

Catalytic cyclization reactions and new stoichiometric skeletal rearrangement cycloisomerizations of 2-ethynylphenyl vinyl ethers containing methyl substituents on the vinyl groups by using [Ru]Cl {[Ru]=Cp(PPh₃)₂Ru, Cp=η⁵-cyclopentadienyl} were observed in MeOH and CH₂Cl₂, respectively. In MeOH, the catalytic cyclization of three different enynes gave the corresponding benzoxepine derivatives in high yields in each case. Interestingly, in the stoichiometric reactions of [Ru]Cl with enynes, two unprecedented rearrangements of enynes were observed in CH₂Cl₂. The presence of a methyl group in the vinyl unit plays a critical role in choosing one of the double bonds of the vinylidene ligand, that is, the Ru=Cα or the Cα=Cβ bond, for the [2+2] cycloaddition in the cycloisomerization processes. Structure determination by single-crystal X-ray diffraction analysis along with various isotope studies corroborated the proposed mechanisms.