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A bio-inspired synthesis of oxindoles by catalytic aerobic dual C-H functionalization of phenols.

ABSTRACT: Nitrogen-containing heterocycles are fundamentally important to the function of pharmaceuticals, agrochemicals and materials. Herein, we report a bio-inspired approach to the synthesis of oxindoles, which couples the energetic requirements of dehydrogenative C-N bond formation to the reduction of molecular oxygen (O₂). Our method is inspired by the biosynthesis of melanin pigments (melanogenesis), but diverges from the biosynthetic polymerization. Mechanistic analysis reveals the involvement of Cu^II-semiquinone radical intermediates, which enable dehydrogenative carbon-heteroatom bond formation that avoids a catechol/quinone redox couple. This mitagates the deleterious polarity reversal that results from phenolic dearomatization, and enables a high-yielding phenolic C-H functionalization under catalytic aerobic conditions. Our work highlights the broad synthetic utility and efficiency of forming C-N bonds via a catalytic aerobic dearomatization of phenols, which is currently an underdeveloped transformation.

SUBMITTER: Huang Z

PROVIDER: S-EPMC5952266 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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A bio-inspired synthesis of oxindoles by catalytic aerobic dual C-H functionalization of phenols.

Huang Zheng Z Askari Mohammad S MS Esguerra Kenneth Virgel N KVN Dai Tian-Yang TY Kwon Ohhyeon O Ottenwaelder Xavier X Lumb Jean-Philip JP

Chemical science 20151006 1

Nitrogen-containing heterocycles are fundamentally important to the function of pharmaceuticals, agrochemicals and materials. Herein, we report a bio-inspired approach to the synthesis of oxindoles, which couples the energetic requirements of dehydrogenative C-N bond formation to the reduction of molecular oxygen (O<sub>2</sub>). Our method is inspired by the biosynthesis of melanin pigments (melanogenesis), but diverges from the biosynthetic polymerization. Mechanistic analysis reveals the invo ...[more]

PMID: 29861988

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Project description:Ceramic materials possessing the properties of high-strength and rigidity are widely used in industry. The shell nacre has a layered structure containing both macroscopic and microscopic levels and is equipped with superior qualities regarding hardness and strength. Therefore, the ceramic composites with a nacre-like layered structure have the potential to be utilized as sliding bearings employed in the harsh conditions of wells. For the purpose of this paper, a porous Al?O? ceramics skeleton with nanometer powder is prepared using the freeze-casting method. Then the porous ceramic skeleton is filled with polymer polymethyl methacrylate (PMMA) through mass polymerization to produce a bionic Al?O?/PMMA composite with a lamellar structure. The properties of the prepared composite are determined by the analysis of micro-hardness, fracture toughness, friction coefficient, wear scar diameter, and the morphology of the worn surface. Consequent results indicate that elevation in the A1?O? powder, which acts as the initial solid phase content, prompts the ceramic slurry to exhibit an increase in viscosity and a gradual decrease in the pore size of the ceramic skeleton. The prepared layered Al?O?/PMMA composite possesses high fracture toughness, which closely resembles that of Al, is approximately four times that of the matrix of the Al?O? ceramics and 16 times that of the PMMA. Three kinds of composites containing different solid phase content are subjected to testing involving lubrication by water-based drilling fluid to determine the friction coefficient of each. The results indicate that an increased load leads to a decreased friction coefficient while the impact of speed is not evident. Under dry conditions, the friction coefficient of three different composites tested, declines with elevated load and speed. With the use of water-based drilling fluid as lubrication, the wear scar diameter increases at higher speed, while dry conditions denote increased load. Abrasive wear is determined to be the principal form of erosion of layered Al?O?/PMMA composites.

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A bio-inspired synthesis of oxindoles by catalytic aerobic dual C-H functionalization of phenols.

Publications

A bio-inspired synthesis of oxindoles by catalytic aerobic dual C-H functionalization of phenols.

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