Cyclization and Subsequent Intermolecular Dehydrative Coupling and Comparative Intramolecular Dehydration of Ruthenium Vinylidene Complexes from Aromatic Propynes Containing Carbonyl Functionalities
Date Issued
2014
Date
2014
Author(s)
Kuo, Cheng-Chen
Abstract
Cyclization of terminal aromatic alkynes containing ortho-substituted aldehyde, ketone or hydroxyl functionality on the aryl ring induced by ruthenium complex is known to proceed via formation of vinylidene intermediate followed by an oxygen attack at Cα to give carbene complexes. However, our development on the coupling of the carbonyl functionality with Cβ of the vinylidene moiety yielded different final products. In the [Ru]-Cl induced ([Ru]=CpRu(PPh3)2) reaction of o-propynyl benzaldehyde 1a the vinylidene complex 2a containing a 1-hydroxyindan moiety, bonded at Cβ and carbonyl carbon, and the dinuclear bisvinylidene complex 3a are isolated. No intramolecular dehydration is possible for 2a. Therefore, the dinuclear complex 3a is produced by a new process of intermolecular dehydrative coupling of 2a yielding a new C-C bond. For aldehyde 1b containing a 1,3-dioxolane group on the aryl ring, the cyclization reaction takes place at Cβ first giving the intramolecular cyclized vinylidene complex 2b’, which similarly undergoes intermolecular coupling to yield the dinuclear bisvinylidene complex 3b’. However, in the reaction of 1c, containing an electron-withdrawing fluoro group in the para-position of aldehyde, with [Ru]-Cl, no further intermolecular coupling happens, instead, only the disubstituted vinylidene complex 2c’ is obtained by intramolecular attack of Cβ onto carbonyl group. Additionally, in the reaction of o-propynylphenyl ketone derivatives 1d-f and 1k-m, the cyclized ruthenium vinylidene complexes 2d-f and 2k-m’, respectively, are also obtained and further intramolecular dehydration takes place in the case of 2d, 2k and 2m’, affording complexes 5d, 5k and 5m. Furthermore, treatment of the o-propynylphenyl α,β-unsaturated ketone 1g-i and 1j with [Ru]-Cl in the presence of NH4PF6 in MeOH afforded the vinylidene complex 6g-i and 7j with 1-benzosuberone moiety. This intramolecular cyclization product was produced by the nucleophilic addition of Cβ onto the alkene part. Interestingly, when heating the 5k in MeOH at 50 °C, the sequential cyclization is proceeded via nucleophilic attack of the unsaturated alkenes onto the electrophilic Cα of vinylidene moiety, giving the demetallation product fluorene 8. Additionally, heating the o-propynylphenyl ketone 1m in CDCl3 with [Ru]-Cl at 50 °C gives the catalytic products 1-benzylidene-3-methyl-1H-isochromene 9. All these reaction products are characterized by spectroscopic methods. In addition, structures of complexes 3a, 5d, 2e and 6h are confirmed by X-ray diffraction analysis.
Subjects
釕金屬
亞乙烯基
環化
脫水
分子間偶合
催化
Type
thesis
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