- Optimizing the crystallization process of conjugated polymer photocatalysts to promote electron transfer and molecular oxygen activation
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Photocatalytic reactive oxygen species (ROS)-induced reactions provide an appealing method to solve the environmental and energy issues, whereas the current oxidation reaction generally suffered from low efficiency and poor selectivity due to uncontrollable O2 activation process. In view of the existence of competitive electron and energy transfer pathway, we propose that highly efficient superoxide radical anion (·O2?) generation can be achieved by optimizing the order degree of the photocatalyst. Herein, by taking carbon nitride polymer as an example, we optimized the crystallization process of carbon nitride polymer by selecting precursors of different polymerization degrees with a molten salt method. Benefiting from the high crystallinity, extended π-conjugated system and strong van der-Waals interactions between interlayers, the modified carbon nitride polymer exhibited accelerated charge transport and enhancement in electron induced molecular oxygen activation reactions under visible light. Consequently, the CCN-P exhibits about 1.5 times higher conversion rate in hydroxylation of phenylboronic acid and over 6-fold faster degradation rate in Rh B organic pollutants photodegradation with respect to pristine carbon nitride. This study provides an in-depth understanding on the optimization of the O2 activation process and the design of advanced photocatalysts.
- Anpo, Masakazu,Cheng, Jiajia,Huang, Caijin,Ou, Honghui,Ren, Wei,Wang, Xinchen
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p. 636 - 645
(2020/07/27)
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- Catalyst-Controlled Regioselective Chlorination of Phenols and Anilines through a Lewis Basic Selenoether Catalyst
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We report a highly efficient ortho-selective electrophilic chlorination of phenols utilizing a Lewis basic selenoether catalyst. The selenoether catalyst resulted in comparable selectivities to our previously reported bis-thiourea ortho-selective catalyst, with a catalyst loading as low as 1%. The new catalytic system also allowed us to extend this chemistry to obtain excellent ortho-selectivities for unprotected anilines. The selectivities of this reaction are up to >20:1 ortho/para, while the innate selectivities for phenols and anilines are approximately 1:4 ortho/para. A series of preliminary studies revealed that the substrates require a hydrogen-bonding moiety for selectivity.
- Dinh, Andrew N.,Maddox, Sean M.,Vaidya, Sagar D.,Saputra, Mirza A.,Nalbandian, Christopher J.,Gustafson, Jeffrey L.
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p. 13895 - 13905
(2020/11/03)
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- The Catalyst-Controlled Regiodivergent Chlorination of Phenols
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Different catalysts are demonstrated to overcome or augment a substrate's innate regioselectivity. Nagasawa's bis-thiourea catalyst was found to overcome the innate para-selectivity of electrophilic phenol chlorination, yielding ortho-chlorinated phenols that are not readily obtainable via canonical electrophilic chlorinations. Conversely, a phosphine sulfide derived from 2,2′-Bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) was found to enhance the innate para-preference of phenol chlorination.
- Maddox, Sean M.,Dinh, Andrew N.,Armenta, Felipe,Um, Joann,Gustafson, Jeffrey L.
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supporting information
p. 5476 - 5479
(2016/11/17)
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- Continuous-flow synthesis of functionalized phenols by aerobic oxidation of grignard reagents
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Phenols are important compounds in chemical industry. An economical and green approach to phenol preparation by the direct oxidation of aryl Grignard reagents using compressed air in continuous gas-liquid segmented flow systems is described. The process tolerates a broad range of functional groups, including oxidation-sensitive functionalities such as alkenes, amines, and thioethers. By integrating a benzyne-mediated in-line generation of arylmagnesium intermediates with the aerobic oxidation, a facile three-step, one-flow process, capable of preparing 2-functionalized phenols in a modular fashion, is established. Putting on airs: Aerobic oxidation of (hetero)aryl Grignard reagents using compressed air proceeds with a gas-liquid continuous-flow system, thus enabling preparation of fucntionalized phenols. By integrating an in-line generation of ArMgBr intermediates with the aerobic oxidation, ortho-functionalized phenols can be assembled. The method demonstrates good functional-group (FG) compatibility, mild reaction conditions, and short reaction times.
- He, Zhi,Jamison, Timothy F.
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supporting information
p. 3353 - 3357
(2014/04/03)
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- 2-(Trimethylsilyl)ethanol as a new alcohol equivalent for copper-catalyzed coupling of aryl iodides
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2-(Trimethylsilyl)ethanol as a new alcohol equivalent has been employed for copper-catalyzed coupling of aryl iodides. Using mild reaction conditions, it has been observed that substituted phenols and phenols with sensitive functional groups can be readily prepared.
- Dibakar, Mullick,Prakash, Anjanappa,Selvakumar, Kumaravel,Ruckmani, Kandasamy,Sivakumar, Manickam
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p. 5338 - 5341
(2011/10/19)
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