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    Home > Conghuan group, Institute of physics and chemistry, Chinese Academy of Sciences: using dye-sensitized semiconductors as visible light catalysts to realize the decarboxylation and alkylation of hydrocarbon bonds

    Conghuan group, Institute of physics and chemistry, Chinese Academy of Sciences: using dye-sensitized semiconductors as visible light catalysts to realize the decarboxylation and alkylation of hydrocarbon bonds

    • Last Update: 2018-06-01
    • Source: Internet
    • Author: User
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    As a clean strategy of organic synthesis, the application of lead visible light catalytic synthesis in selective chemical conversion is increasing day by day In this kind of catalytic reactions, homogeneous metal complexes and organic dyes, as common visible light catalysts, have been widely used in synthesis reactions; in contrast, the synthesis methods of heterogeneous photocatalysis, which are low cost, easy to operate and easy to recover, still have a large expansion space in the diversity and selectivity of reactions Recently, inspired by the dye sensitization system, Conghuan group of Institute of physical and chemical technology of Chinese Academy of Sciences has used cheap and heavy metal free organic small molecule sensitizer and nano titanium dioxide to jointly catalyze a series of reactions The catalytic efficiency and selectivity are much higher than that of the two alone At the same time, it overcomes the weakness of poor reaction selectivity, and realizes the high-efficient and precise synthesis of target products under mild conditions At present, the research group has successively developed the oxidation reaction of benzyl ether (ACS catalyst 2017, 7, 8134), the addition reaction of olefin atom transfer radical (chemsuschem 2017, 10, 4461), and the decarboxylation alkylation reaction of SP 3 hydrocarbon bond (org Lett 2018, 20, DOI: 10.1021/acs.orglett.8b01077) About researcher Cong Huan, he graduated from Peking University in 2006 (Tutor: academician Xi Zhenfeng), received his Ph.D from Boston University in 2011 (Tutor: Professor John A Porco), and engaged in post doctoral research at MIT and Caltech from 2011 to 2015 (Tutor: Gregory C Professor Fu), who was selected into the 11th batch of "youth thousand talents plan" of the central organization department in 2015, was incorporated into the Institute of physical and chemical technology of the Chinese Academy of Sciences to carry out independent research The research direction is photochemical synthesis of functional organic molecules, among which the synthesis of carbon nanorings by photochemical strategies has been published in J am Chem SOC (J am Chem SOC 2016, 138, 11144) He has won the "Kenneth Hancock Memorial Award" (2011) of the president of the United States and "Thieme Chemistry Journals Award" (2017) of Germany Cutting edge scientific research achievements: using dye-sensitized semiconductor as visible light catalyst to realize the decarboxylation and alkylation of C-H bond, the author uses P25 titanium dioxide sensitized by erythritol B as photocatalyst to realize the visible driven p-tetrahydroisoquinoline derivative SP 3 This reaction has many advantages, such as wide range of substrates, low cost, no heavy metals, mild conditions and so on The reaction conditions were optimized When n-acyloxyphthalimide was used as alkylating agent and erythritol B and P25 titanium dioxide were used as co photocatalysts, the alkylation products could be obtained in almost quantitative yield under blue light irradiation Blank experiments showed that visible light, dye and semiconductor were all necessary conditions Figure 1 Optimization of reaction conditions (source: org Lett.) through the expansion of the substrate, the author found that the first, second and third alkylation products can be obtained smoothly, and the reaction has excellent functional compatibility Fig 2 Expansion of reaction substrate (source: org Lett.) Fig 3 Free radical clock experiment (source: org Lett.) free radical clock experiment (source: org Lett.) results show that the substrate with cyclopropyl group can completely open the ring to generate end olefin products in the reaction Therefore, the author proposed the possible reaction mechanism: under the visible light irradiation, the excited dye (dye *) transfers the electron to the titanium dioxide conduction band (CB), the raw material 2 obtains the electron under the hydrogen bond promotion and transforms it into the free radical anion intermediate a, and then undergoes the N-O bond splitting to remove the o-phthalimide anion and carbon dioxide to obtain the alkyl free radical B In addition, raw material 1 undergoes a single electron transfer (set) and deproton process to form free radical D Free radicals B and D form target product 3 Figure 4 Possible reaction mechanism (source: org Lett) The research results were recently published in organic letters (DOI: 10.1021 / ACS Orglett 8b01077) Ren Li, Ph.D candidate of Institute of physics and chemistry, was the first author of this paper The research was supported by the "youth thousand talents plan" of the Central Organization Department, the National Natural Science Foundation, the director's fund of the Chinese Academy of Sciences and the Institute of physics and chemistry Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeango app, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.
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