Abstract:An efficient oxidation of sp3 C–H bonds to esters and ketones has been developed using AgI/BiVO4 as the photocatalyst and O2 as the oxidant in water.
“…12 ). Four obvious signals with Zn/NC-950 in methanol were obtained, which confirmed the existence of DMPO- • 55 , 56 . Fig.…”
Section: Resultsmentioning
confidence: 58%
“…Subsequently, two reaction pathways proceeded to form the desired ester. In one pathway (Route A), II might be homolytically cleaved to the corresponding α -oxy radical III, and then cleaved to ketones/aldehydes IV and benzaldehyde radical species V via β -scission 56 . The V was then reacted with R-OH, giving ester as the final products and the ketones/aldehydes as the split products.…”
Selective cleavage of C-C bonds is very important in organic chemistry, but remains challenging because of their inert chemical nature. Herein, we report that Zn/NC-X catalysts, in which Zn2+ coordinate with N species on microporous N-doped carbon (NC) and X denotes the pyrolysis temperature, can effectively catalyze aerobic oxidative cleavage of C(CO)-C bonds and quantitatively convert acetophenone to methyl benzoate with a yield of 99% at 100 °C. The Zn/NC-950 can be applied for a wide scope of acetophenone derivatives as well as more challenging alkyl ketones. Detail mechanistic investigations reveal that the catalytic performance of Zn/NC-950 can be attributed to the coordination between Zn2+ and N species to change the electronic state of the metal, synergetic effect of the Zn single sites with their surrounding N atoms, as well as the microporous structure with the high surface area and structural defects of the NC.
“…12 ). Four obvious signals with Zn/NC-950 in methanol were obtained, which confirmed the existence of DMPO- • 55 , 56 . Fig.…”
Section: Resultsmentioning
confidence: 58%
“…Subsequently, two reaction pathways proceeded to form the desired ester. In one pathway (Route A), II might be homolytically cleaved to the corresponding α -oxy radical III, and then cleaved to ketones/aldehydes IV and benzaldehyde radical species V via β -scission 56 . The V was then reacted with R-OH, giving ester as the final products and the ketones/aldehydes as the split products.…”
Selective cleavage of C-C bonds is very important in organic chemistry, but remains challenging because of their inert chemical nature. Herein, we report that Zn/NC-X catalysts, in which Zn2+ coordinate with N species on microporous N-doped carbon (NC) and X denotes the pyrolysis temperature, can effectively catalyze aerobic oxidative cleavage of C(CO)-C bonds and quantitatively convert acetophenone to methyl benzoate with a yield of 99% at 100 °C. The Zn/NC-950 can be applied for a wide scope of acetophenone derivatives as well as more challenging alkyl ketones. Detail mechanistic investigations reveal that the catalytic performance of Zn/NC-950 can be attributed to the coordination between Zn2+ and N species to change the electronic state of the metal, synergetic effect of the Zn single sites with their surrounding N atoms, as well as the microporous structure with the high surface area and structural defects of the NC.
“…As shown in Figure 9, six obvious signals were observed, which can be attributed to the DMPO-* O 2 À complex. [41,42] Thus, the control experiment as well as the EPR measurement both confirmed that the active oxygen species was * O 2 À . As far as the activation of O 2 by nitrogen-doped carbon materials, it has been widely reported that the sp 2 carbon, [43] edges and defects, [22,44] epoxy, hydroxyl and carboxyl groups, [22] graphitic-N, [23,44] and carbon atoms adjacent to the graphitic-N [45] all have the capacity of activating O 2 .…”
N‐heteroarenes represents one of the most important chemicals in pharmaceuticals and other bio‐active molecules, which can be easily accessed from the oxidation of N‐heterocycles over metal catalysts. Herein, the metal‐free oxidative dehydrogenation of N‐heterocycles into N‐heteroarenes was developed using molecular oxygen as the terminal oxidant. The nitrogen‐doped carbon materials were facilely prepared via the simple pyrolysis process using biomass (carboxymethyl cellulose sodium) and dicyandiamide as the carbon and nitrogen source, respectively, and they were discovered to be robust for the oxidative dehydrogenation of N‐heterocycles into N‐heteroarenes under mild conditions (80 °C under 1 bar O2) with water as the green solvent. Diverse N‐heterocycles including 1,2,3,4‐tetrahydroisoquinolines, indolines and 1,2,3,4‐tetrahydroquinoxalines were smoothly converted into N‐heteroarenes with high to excellent yields (76–>99 %). Superoxide radical (⋅O2−) and hydroxyl radical (⋅OH) were probed as the reactive oxygen species for the oxidation of N‐heterocycles into N‐heteroarenes. More importantly, the nitrogen‐doped carbon catalyst can be reused with a high stability. The method provides an environmentally friendly and economical route to access important N‐hetero‐aromatic commodities.
“…In a recent publication from Ren and collaborators [44] AgI/BiVO 4 composites have been employed in the photooxidation of alkylbenzenes and benzyl ethers (Scheme 12). AgI and BiVO 4 are both exited by visible‐light and are able, to a certain extent, to catalyse the reaction giving the oxidation product in low yields or traces, respectively.…”
Transition metal-catalysed processes have been widely used for the functionalization of inert CÀ H bonds. Strategies for the functionalization of the benzylic CÀ H position having a relatively weak CÀ H bond (bond dissociation energy~80-90 kcal/mol) differ from the inert aliphatic and aromatic CÀ H positions with stronger CÀ H bonds. The recent advances in the direct activation of the benzylic position through the generation of C(sp 3) radicals have demonstrated the potential of electrochemistry and photochemistry as a means for constructing new chemical bonds. This review will cover the recent progress of benzylic CÀ H functionalization through organic radical strategies employing photochemistry and electrochemistry as sustainable tools. In addition, the mechanistic details of the typical reactions have been included which, in turn, will help the researchers to look at this promising area from a different perspective towards new discoveries and often hidden opportunities. 2.1. C(sp 3)À C Bond Formation 2.2. C(sp 2)À O and C(sp 3)À O Bond Formation 2.3. C(sp 3)À N Bond Formation 2.4. C(sp 3)À S Bond Formation 2.5. C(sp 3)À Halogen Bond Formation 3. Electrochemical Benzylic C(sp 3)À H Functionalization 3.1. C(sp 3)À C Bond Formation 3.2. C(sp 3)À O Bond Formation 3.3. C(sp 3)À N Bond Formation 3.4. C(sp 3)À P Bond Formation 3.5. C(sp 3)À Halogen Bond Formation 4. Benzylic C(sp 3)À H Functionalization via Synthetic Photoelectrochemistry 5. Conclusions and Outlook
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
