5048-02-2Relevant academic research and scientific papers
Chemoselective oxidative generation of ortho-quinone methides and tandem transformations
Ishihara, Kazuaki,Kondo, Ryutaro,Nishioka, Kohei,Uyanik, Muhammet
, p. 353 - 362 (2020/04/09)
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.].
Phenolic Oxidation Using H2O2 via in Situ Generated para-Quinone Methides for the Preparation of para-Spiroepoxydienones
McLaughlin, Michael F.,Massolo, Elisabetta,Cope, Thomas A.,Johnson, Jeffrey S.
, p. 6504 - 6507 (2019/09/04)
Phenols are attractive starting materials for the preparation of highly substituted cyclohexane rings via dearomative processes. Herein we report an efficient preparation of dearomatized 1-oxaspiro[2.5]octa-4,7-dien-6-ones (para-spiroepoxydienones) via the nucleophilic epoxidation of in situ generated para-quinone methides from 4-(hydroxymethyl)phenols using aqueous H2O2. The developed protocol bypasses the need for stoichiometric bismuth reagents or diazomethane, which are frequently deployed for p-spiroepoxydienone preparation. The p-spiroepoxydienones are further elaborated in numerous downstream complexity-building transformations.
Selective benzylic C-C coupling catalyzed by a bioinspired dicopper complex
Prokofieva, Angelina,Prikhod'ko, Alexander I.,Dechert, Sebastian,Meyer, Franc
, p. 1005 - 1007 (2008/09/21)
A highly preorganized bioinspired dicopper complex with imidazole ligation catalyzes the selective benzylic para-C-H activation of 2,4,6-trimethylphenol under aerobic conditions, yielding either the stilbenequinone or 4-methoxymethyl-2,6-dimethylphenol depending on the solvent used. The Royal Society of Chemistry.
Selective copper(II)-mediated oxidative coupling of a nucleophilic reagent to the para-methyl group of 2,4,6-trimethylphenol
Boldron, Christophe,Oezalp-Yaman, Seniz,Gamez, Patrick,Tooke, Duncan M.,Spek, Anthony L.,Reedijk, Jan
, p. 3535 - 3541 (2007/10/03)
A copper(II) neocuproine system has been developed for the efficient and very selective 1,6-addition of a nucleophile to the para-methyl group of 2,4,6-trimethylphenol. Crystallographic and spectroscopic data point towards the involvement of a μ-methoxo-μ-phenoxo-bridged copper species which appears to generate a highly reactive quinone methide intermediate that can be attacked by a nucleophilic reagent. The Royal Society of Chemistry 2005.
Copper-mediated selective oxidation of a C-H bond
Boldron, Christophe,Gamez, Patrick,Tooke, Duncan M.,Spek, Anthony L.,Reedijk, Jan
, p. 3585 - 3587 (2007/10/03)
(Chemical Equation Presented) An environmentally friendly procedure has been developed for the oxidation of 2,4,6-trimethylpheriol (TMP) at the para Csp3-H bond. Upon reaction with H2O2 in the presence of catalytic amounts of CuII and neocuproine in methanol at 65°C, 4-(methoxymethyl)-2,6-dimethylphenol (MDP) or 4-hydroxy-3,5- dimethylbenzaldehyde (HDB) is formed (see reaction).
The Oxidation of 2,4,6-Trimethylphenol with Molecular Oxygen Catalyzed by a Copper(II)-Oxime or Copper(II)-Amine System
Shimizu, Masao,Watanabe, Yoshihito,Orita, Hideo,Hayakawa, Takashi,Takehira, Katsuomi
, p. 251 - 257 (2007/10/02)
2,4,6-Trimethylphenol (1a) was selectively oxidized to 3,5-dimethyl-4-hydroxybenzaldehyde (2a) by molecular oxygen in the presence of a copper(II) chloride-oxime or copper(II) chloride-amine catalyst in alcohol at ambient temperature.When an acid was present in the catalyst system, the formation of both 2,6-dimethyl-p-benzoquinone (3) and a formaldehyde dialkyl acetal was accelerated.It is likely that 2a is produced by way of the formation of a quinonemethide intermediate, followed by a repeated 1,6-addition of alcohol on the intermediate to form a 4-(alkoxymethyl)-2,6-dimethylphenol (5a), and then 3,5-dimethyl-4-hydroxybenzaldehyde dialkyl acetal, which would be hydrolyzed to 2a.When the reaction time was shortened, 5a was isolated in good yield.Oxidations of the other p-methyl-substituted phenols were also examined using the present oxidation system.
A Facile Synthesis of 4-Alkoxymethylphenols by a Copper(II)-Acetoxime Catalyst/O2 System
Shimizu, Masao,Watanabe, Yoshihito,Orita, Hideo,Hayakawa, Takashi,Takehira, Katsuomi
, p. 2053 - 2056 (2007/10/02)
4-Alkoxymethyl-2,6-dimethylphenols were synthesized from 2,4,6-trimethylphenol in good yields by a copper(II) chloride-acetoxime catalyst/molecular oxygen system in alcohols at ambient temperature.The oxidation of the other p-methylsubstituted phenols were also examined.
Oxidation products of paramethyl-substituted hindered phenols
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, (2008/06/13)
Paramethyl-substituted hindered phenols are selectively oxidized by contacting with an oxidizing agent at elevated temperatures in the presence of a heterogeneous oxidative coupling catalyst. In the absence of an optional nucleophile the products comprise carbon-carbon oxidative coupling products. In the presence of a nucleophile, addition products result that may be further oxidized by continued exposure to the oxidizing agent to yield substituted p-hydroxybenzaldehydes.
THE CHEMISTRY OF PENTAVALENT ORGANOBISMUTH REAGENTS. PART XI. REACTIONS WITH STERICALLY HINDERED PHENOLS.
Barton, Derek H. R.,Finet, Jean-Pierre,Gianotti, Charles,Halley, Frank
, p. 4483 - 4494 (2007/10/02)
The reactivity of BiV reagents towards very hindered phenols with tert.-butyl groups at 2 and 6 under basic conditions has been studied.Unexpected phenylation at the 4-position and, in several cases, replacement of a tert.-butyl group by phenyl have been observed.The mechanism of these unexpected reactions has been discussed.
THE CHEMISTRY OF PENTAVALENT ORGANOBISMUTH REAGENTS. PART X. STUDIES ON THE PHENYLATION AND OXIDATION OF PHENOLS
Barton, Derek H. R.,Yadav-Bhatnagar, Neerja,Finet, Jean-Pierre,Khamsi, Jamal,Motherwell, William B.,Stanforth, Stephen P.
, p. 323 - 332 (2007/10/02)
The influence of the substituents on the phenol on the regiochemistry of the arylation reactions with Ph3BiCl2 and other bismuth reagents has been studied.O-Phenylation occurs with phenols substituted with electron-withdrawing groups.Electron-donating substituted phenols undergo ortho C-phenylation.Oxidative dimerisation has been observed with 2,6-dialkyl phenols.
