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Cyclization of 2‐Ethynylphenyl Vinyl Ether Catalyzed by a Ruthenium Complex: Mechanism of Catalytic Cyclization and Stoichiometric Cycloisomerization
Author(s) -
Chen ChiRen,
Lai YingXuan,
Wu RongYu,
Liu YiHung,
Lin YingChih
Publication year - 2016
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201600428
Subject(s) - cycloisomerization , chemistry , ruthenium , catalysis , cycloaddition , vinyl ether , cyclopentadienyl complex , stoichiometry , medicinal chemistry , ether , double bond , stereochemistry , polymer chemistry , organic chemistry , copolymer , polymer
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(PPh 3 ) 2 Ru, Cp=η 5 ‐cyclopentadienyl} were observed in MeOH and CH 2 Cl 2 , 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 CH 2 Cl 2 . 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 C α =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.