Reaction discovery using acetylene gas as the chemical feedstock accelerated by the “stop-flow” micro-tubing reactor system

Xue, Fei; Deng, Hong‐Ping; Xue, Chengwen; Mohamed, Dara Khairunnisa Binte; Tang, Karen Yuanting; Wu, Jie

doi:10.1039/c7sc00408g

Cited by 76 publications

(40 citation statements)

References 28 publications

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“…The SFMT reactor was thus applied to keep ethylene in the reaction solution at high temperature and high pressure for the substrate scope evaluation of 4 (condition D). 23 The SFMT reactor proved to be efficient for the generation of 2,3-diarylbutanes (4a-4m) from a wide range of paraor metasubstituted aryl iodides and bromides (Scheme 1B). Further substrate expansion to arene-fused heterocycles was investigated, and 4n-4t were generated effectively.…”

Section: Reaction Scope Investigationmentioning

confidence: 99%

“…[18][19][20][21][22] Our group has recently developed a ''stopflow'' micro-tubing (SFMT) reactor for efficient screening of gas-involved photomediated transformations in a convenient and safe manner. 23 As part of our ongoing interests in developing visible-light-promoted transformations using inexpensive gaseous feedstocks, [23][24][25] we herein report the light-mediated ethylene difunctionalization through the synergistic combination of photoredox and Ni catalysis. Assisted by photocatalysts with different redox potentials, Ni-catalyzed reductive coupling between aryl halides and ethylene produced 1,2-diarylethanes, 1,4-diarylbutanes, and 2,3-diarylbutanes in a highly selective manner ( Figure 1C).…”

Section: Introductionmentioning

confidence: 99%

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Photoredox-Catalysis-Modulated, Nickel-Catalyzed Divergent Difunctionalization of Ethylene

Luo

Cheo

et al. 2019

Chem

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112

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Functionalization of ethylene without polymerization is challenging under photoirradiation conditions. We have demonstrated that the photo-transformation of ethylene can be controllable by merging photoredox and transition-metal catalysis. In our study, the use of different photoredox catalysts was able to modulate the oxidation state of the nickel catalyst. Through different oxidation states, the nickel-catalyzed couplings proceeded via distinct pathways to generate divergent ethylene difunctionalization products selectively from the same feedstock.

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Section: Reaction Scope Investigationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photoredox-Catalysis-Modulated, Nickel-Catalyzed Divergent Difunctionalization of Ethylene

Luo

Cheo

et al. 2019

Chem

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112

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“…SCE) and suitability for oxidizing Cl anion to Cl radical (E ox (Cl À /Cl · ) =+2.03 Vv s. SCE). [13] As part of our ongoing interest in developing visible-light-promoted transformations using readily available C(sp 3 ) À Hb onds as the latent nucleophilic handles, [7,14] we herein report am etal-free C À Ha lkylation and allylation assisted by microtubing reactors with HCl as aH AT catalyst precursor in conjunction with Mes-Acr + as aphotoredox catalyst (Scheme 2c). [9] Continuous microflow technologies have provided effective platforms for photochemical synthesis owing to the improved light penetration associated with microtubing reactors.…”

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confidence: 99%

Microtubing‐Reactor‐Assisted Aliphatic C−H Functionalization with HCl as a Hydrogen‐Atom‐Transfer Catalyst Precursor in Conjunction with an Organic Photoredox Catalyst

2018

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Chlorine radical, which is classically generated by the homolysis of Cl under UV irradiation, can abstract a hydrogen atom from an unactivated C(sp )-H bond. We herein demonstrate the use of HCl as an effective hydrogen-atom-transfer catalyst precursor activated by an organic acridinium photoredox catalyst under visible-light irradiation for C-H alkylation and allylation. The key to success relied on the utilization of microtubing reactors to maintain the volatile HCl catalyst. This photomediated chlorine-based C-H activation protocol is effective for a variety of unactivated C(sp )-H bond patterns, even with primary C(sp )-H bonds, as in ethane. The merit of this strategy is illustrated by rapid access to several pharmaceutical drugs from abundant unfunctionalized alkane feedstocks.

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“…[12] Our research group recently developed a" stopflow" microtubing (SFMT) reactor for efficient screening of photomediated transformations involving gases in ac onvenient and effective manner. [13] As part of our ongoing interest in developing visible-light-promoted transformations using readily available C(sp 3 ) À Hb onds as the latent nucleophilic handles, [7,14] we herein report am etal-free C À Ha lkylation and allylation assisted by microtubing reactors with HCl as aH AT catalyst precursor in conjunction with Mes-Acr + as aphotoredox catalyst (Scheme 2c). Thehigh efficiency relied on the unique advantages provided by the microtubing reactors.…”

mentioning

confidence: 99%

Microtubing‐Reactor‐Assisted Aliphatic C−H Functionalization with HCl as a Hydrogen‐Atom‐Transfer Catalyst Precursor in Conjunction with an Organic Photoredox Catalyst

Deng

Zhou

2018

Angewandte Chemie

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Chlorine radical, which is classically generated by the homolysis of Cl 2 under UV irradiation, can abstract ah ydrogen atom from an unactivated C(sp 3 )ÀHb ond. We herein demonstrate the use of HCl as an effective hydrogenatom-transfer catalyst precursor activated by an organic acridinium photoredoxc atalyst under visible-light irradiation for C À Halkylation and allylation. The key to success relied on the utilization of microtubing reactors to maintain the volatile HCl catalyst. This photomediated chlorine-based CÀHactivation protocol is effective for avariety of unactivated C(sp 3 )ÀH bond patterns,e ven with primary C(sp 3 )ÀHb onds,a si n ethane.The merit of this strategy is illustrated by rapid access to several pharmaceutical drugs from abundant unfunctionalized alkane feedstocks.Dramatic developments in photocatalysis over the past decade have enabled previously inaccessible transformations. [1] In particular,t he synergistic combination of photoredox catalysts and hydrogen-atom-transfer (HAT) catalysts has offered enormous opportunities for C(sp 3 ) À Ha ctivation. [2] In general, upon irradiation with light, the activated photocatalyst can oxidize the HATc atalyst through singleelectron transfer (SET) to form ahydrogen abstractor,either in the presence or absence of abase;the hydrogen abstractor will abstract ah ydrogen atom to deliver ac arbon radical to enable C À Hactivation (Scheme 1a). In this context, avariety of HATc atalysts based on S( thiols), [3] N( quinuclidines, sulfonamides), [4] and O( benzoates, N-hydroxides) [5] have been developed (Scheme 1b). However, the development of readily available and highly efficient catalytic systems that accommodate aw ide range of CÀHp atterns without the requirement of stoichiometric amounts of additives is still highly desirable.Chlorine radical, classically generated by the homolysis of Cl 2 under UV irradiation, represents another heteroatomcentered radical capable of abstracting hydrogen atoms from unactivated aliphatic CÀHb onds.H owever,i th as not been widely recognized as aH AT catalyst under conditions of visible-light irradiation. In this regard, Doyle and co-workers and our group recently demonstrated the generation of chlorine radical by photolysis of aNi III chloride intermediate generated by photoredox-mediated single-electron oxidation of aNi II precursor and showed that it could activate C(sp 3 )ÀH bonds for arylation [6] and hydroalkylation of alkynes, [7] respectively (Scheme 2a). [8] However,t he former reaction uses stoichiometric amounts of chloride compounds,a nd the latter suffered from limited scope with respect to the C À H substrate.B oth methods required excess amounts of CÀH substrates (! 10 equiv) for effective transformations. Scheme 1. Synergistic merging of photoredox and HATcatalysis.

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Reaction discovery using acetylene gas as the chemical feedstock accelerated by the “stop-flow” micro-tubing reactor system

Abstract: A “stop-flow” micro-tubing reactor system was designed for accelerating reaction discovery using flammable acetylene gas as the feedstock.

Cited by 76 publications

References 28 publications

Photoredox-Catalysis-Modulated, Nickel-Catalyzed Divergent Difunctionalization of Ethylene

Photoredox-Catalysis-Modulated, Nickel-Catalyzed Divergent Difunctionalization of Ethylene

Microtubing‐Reactor‐Assisted Aliphatic C−H Functionalization with HCl as a Hydrogen‐Atom‐Transfer Catalyst Precursor in Conjunction with an Organic Photoredox Catalyst

Microtubing‐Reactor‐Assisted Aliphatic C−H Functionalization with HCl as a Hydrogen‐Atom‐Transfer Catalyst Precursor in Conjunction with an Organic Photoredox Catalyst

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