- Chemoselective oxidative generation of ortho-quinone methides and tandem transformations
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ortho-Quinone methides are useful transient synthetic intermediates in organic synthesis. These species are most often generated in situ by the acid- or base-mediated transformation of phenols that have been pre-functionalized at a benzylic position, or by biomimetic oxidation of the corresponding ortho-alkylphenols with metal oxidants or transition-metal complexes. Here we describe a method for the transition-metal-free oxidative generation of o-QMs from ortho-alkylarenols, using hypoiodite catalysis under nearly neutral conditions, which can then be applied in one-pot tandem reactions. This method for the chemoselective oxidative generation of ortho-quinone methides may prove superior to previous methods with respect to environmental issues and scope, and can be applied to various tandem reactions such as inter- or intramolecular [4 + 2] cycloaddition, oxa-6π-electrocyclization, conjugate addition and spiroepoxidation. [Figure not available: see fulltext.].
- Ishihara, Kazuaki,Kondo, Ryutaro,Nishioka, Kohei,Uyanik, Muhammet
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p. 353 - 362
(2020/04/09)
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- Efficient Synthesis of Chromenes from Vinyl o -Quinone Methides via a Bronsted Acid Catalyzed Electrocyclization Process
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An efficient approach for the synthesis of chromene derivatives from vinyl o -quinone methides was established via a Bronsted acid catalyzed electrocyclization. By using this methodology, a series of structurally diversified chromenes was synthesized in a highly atom-economic and environmentally benign manner with generally good to excellent yields (up to 98% yield). This reaction will not only provide an efficient method for the construction of chromene scaffolds, but also enrich the research area of o -quinone methides.
- Liu, Si-Jia,Jiang, Xiao-Li,Wu, Shu-Fang,Tu, Man-Su,Mei, Guang-Jian,Shi, Feng
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p. 2416 - 2422
(2018/05/03)
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- Mechanistic investigations of the acid-catalyzed cyclization of a vinyl ortho-quinone methide
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A study was conducted to perform mechanistic investigations of the acid-catalyzed cyclization of a vinyl ortho-Quinone methide (QM). The study focused on mechanistic investigations of the acid-catalyzed cyclization of a vinyl ortho-Quinone methide, as led to the formation of chromenes. Vinyl o-QM was prepared through oxidation of phenol 3, while the E configuration of the exo-alkylidene bond was established by detailed nuclear magnetic resonance (NMR) studies and X-ray crystallography. The structure of the dimer was also confirmed by X-ray crystallography. Kinetic investigation of the uncatalyzed cyclization of Vinyl o-QM and chromene revealed the sensitivity of the rate of the reaction to light, oxygen, and adventitious acid, studying the reactivity of o-QM.
- Bishop, Lee M.,Winkler, Michael,Houk, Kendall N.,Bergman, Robert G.,Trauner, Dirk
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supporting information; experimental part
p. 5405 - 5408
(2009/06/20)
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