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In view of the widespread significance of amide functional groups in organic synthesis and pharmaceutical studies, an efficient and practical synthetic protocol that avoids the use of stoichiometric activating reagents or metallic reductants is highly desirable. A straight-forward pathway to access amides from abundant chemical feedstock would offer a strategic advantage in the synthesis of complex amides. We herein disclose a direct reductive amidation reaction using readily available aldehydes and nitroarenes enabled by photo-mediated hydrogen atom transfer catalysis. It avoids the use of metallic reductants and production of toxic chemical waste. While aldehydes represent a classic class of electrophilic synthons, the corresponding nucleophilic acyl radicals could be directly accessed by photo hydrogen atom transfer catalysis, enabling polarity inversion. Our method provides an orthogonal strategy to conventional amide couplings, tolerating nucleophilic substituents such as free alcohols and sensitive functional groups to amines such as carbonyl or formyl groups. The synthetic utilization of this reductive amidation is demonstrated by the late-stage modification of complex biologically active molecules and direct access of drug molecules leflunomide and lidocaine.

We report a general, practical, and scalable means of preparing deuterated aldehydes from aromatic and aliphatic carboxylic acids with D2 O as an inexpensive deuterium source. The use of Ph3 P as an O-atom transfer reagent can facilitate the deoxygenation of aromatic acids, while Ph2 POEt is a better O-atom transfer reagent for aliphatic acids. The highly precise deoxygenation of complex carboxylic acids makes this protocol promising for late-stage deoxygenative deuteration of natural product derivatives and pharmaceutical compounds.

The construction of an aryl ketone structural unit by means of catalytic carbon–carbon coupling reactions represents the state-of-the-art in organic chemistry. Herein we achieved the direct deoxygenative ketone synthesis in aqueous solution from readily available aromatic carboxylic acids and alkenes, affording structurally diverse ketones in moderate to good yields. Visible-light photoredox catalysis enables the direct deoxygenation of acids as acyl sources with triphenylphosphine and represents a distinct perspective on activation. The synthetic robustness is supported by the late-stage modification of several pharmaceutical compounds and complex molecules. This ketone synthetic strategy is further applied to the synthesis of the drug zolpidem in three steps with 50% total yield and a concise construction of cyclophane-braced 18–20 membered macrocycloketones. It represents not only the advancement for the streamlined synthesis of aromatic ketones from feedstock chemicals, but also a photoredox radical activation mode beyond the redox potential of carboxylic acids., Synthesis of aryl ketones can be generally achieved via C–C coupling strategies. Here, the authors show a deoxygenative coupling of carboxylic acids and alkenes enabled by photoredox catalysis and report a wide scope of products, including bioactive and macrocyclic ketones.

A practical photoredox and cobalt co-catalyzed C(sp2)–H functionalization/C–O bond formation is described herein, with dihydrogen as the only by-product. A variety of lactone products can be successfully constructed under oxidant- and acceptor-free conditions with good functional group tolerance and high yield. This protocol also provides a facile route to remote hydroxylated arenes and chromene.

A hydroacylation reaction of alkenes has been achieved employing readily available carboxylic acids as the acyl source and hydrosilanes as a hydrogen source via photoredox catalysis. The combination of both single electron transfer and hydrogen atom transfer steps has dramatically expanded new applications of carboxylic acids in organic synthesis. The protocol also features extremely mild conditions, broad substrate scope, and good functional group tolerance, affording a novel and convenient approach to hydroacylation of alkenes.

An unprecedented deoxygenative arylation of aromatic carboxylic acids has been achieved, allowing the construction of an enhanced library of unsymmetrical diaryl ketones. The synergistic photoredox catalysis and phosphoranyl radical chemistry allows for precise cleavage of a stronger C-O bond and formation of a weaker C-C bond by 1,5-aryl migration under mild reaction conditions. This new protocol is independent of substrate redox-potential, electronic, and substituent effects. It affords a general and promising access to 60 examples of synthetically versatile o-amino and o-hydroxy diaryl ketones under redox-neutral conditions. Furthermore, it also brings one concise route to the total synthesis of quinolone alkaloid, (±)-yaequinolone A2, and a viridicatin derivative in satisfying yields.

The reductive single electron transfer (SET) umpolung amination of aldehyde-derived hydrazones has been developed through visible-light-promoted photoredox catalysis. The ideal transformation of hydrazones into the corresponding hydrazonamide through selective carbon-hydrogen (C-H) bond functionalization represents one of the most step- and atom-economical methods. This SET umpolung strategy features mild conditions and a remarkably broad substrate scope, offering an entirely new substrate class to direct C-H amination.

The novel cascade photoredox/iodide catalytic system enables the alkene to serve as a radical acceptor capable of achieving aminodifluoroalkylation of alkenes. Cheap iodide salts play a vital role in this reaction, which could tune carbocation reactivity through reversible C-I bond formation for controlling reaction selectivity, and a series of competitive reactions are completely eliminated in the presence of multiple reactivity pathways. The present dual catalytic protocol affords a very convenient method for direct synthesis of various difluoro-γ-lactams from simple and readily available starting materials under mild reaction conditions.

A novel visible light photoredox catalysis three-component 1,2-difluoroalkylarylation of styrenes was disclosed, and two new C–C bonds were generated in a single step through regioselective incorporation of a CF2 group and a variety of indoles to CC bonds. The well-designed photoredox system achieved the synthesis of a series of difluoro-containing indole derivatives with mild conditions and a broad substrate scope.

Visible light induced photoredox catalysis is an efficient method for radical activation. Herein, we report the photoredox catalysis involving an intramolecular radical-radical coupling reaction that proceeds through a biradical intermediate. This protocol represents a new synthetic route to construct multi-substituted N-heterocycles. Four, five and six-membered N-heterocyclic structures with a quaternary carbon center are accessible under mild conditions.

A novel approach to obtain functionalized tetrazoles by a [3+2] cycloaddition of azide with aldehyde hydrazone is reported. This reaction features a broad substrate scope and mild reaction conditions through an aminyl radical-polar crossover strategy.

Examination paper analysis is important for students to improve their learning efficiency. Traditional paper examination papers are difficult to sort out, which makes collecting mistakes for future review both time-consuming and laborious, either by handwriting or existed software tools. To easy the process, we propose a layout analysis method combined with the conditional generative adversarial network (CGAN). The traditional semantic segmentation structure is improved and used as a generator in the network, while a discriminator is designed to make the segmentation results more accurate. The motivation is that the discriminator can judge the authenticity of the image, so it can help reduce the unreasonable phenomenon in the semantic segmentation results of the generator. The experimental results show that by this method the examination paper image can be welly split into various components, which provides convenience for further sorting and analysis of the examination paper images.

We report a general, practical, and scalable means of preparing deuterated aldehydes from aromatic and aliphatic carboxylic acids with D

C-1-monofluoromethylated tetrahydroisoquinolines are obtained by visible-light photoredox-catalyzed reaction of tetrahydroisoquinolines with β-fluorinated gem-diols as CF-source under mild reaction conditions.

An efficient deoxygenative radical cyclization reaction has been reported for the synthesis of fluorenones by employing various biarylcarboxylic acids via photoredox catalysis. Attractive features of this process include generation of acyl radical, which quickly underdone intramolecular radical cyclization. This method marks the first photocatalytic intramolecular acyl radical coupling for constructing carbon–carbon bond, which further synthesizes the valuable fluorenone products with mild conditions, good yields, and good functional-group compatibility.

The direct reduction of carboxylic acids to aldehydes with hydrosilane was achieved through visible light photoredox catalysis. The combination of both single electron transfer and hydrogen atom transfer steps offers a novel and convenient approach to selective reduction of carboxylic acids to aldehydes. The method also features mild conditions, high yields, broad substrate scope, and good functional group tolerance, such as alkyne, ester, ketone, amide and amine groups.

Domino-fluorination–protodefluorination decarboxylative cross-coupling of α-keto acids with styrene has been developed via photoredox catalysis. The critical part of this strategy is the formation of the carbon–fluorine (C–F) bond by the capture of a carbon-centered radical intermediate, which will overcome side reactions during the styrene radical functionalization process. Experimental studies have provided evidence indicating a domino-fluorination–protodefluorination pathway with α-keto acid initiating the photoredox cycle. The present catalytic protocol also affords a novel approach for the construction of α,β-unsaturated ketones under mild conditions.

The novel cascade photoredox/iodide catalytic system enables the alkene to serve as a radical acceptor capable of achieving aminodifluoroalkylation of alkenes. Cheap iodide salts play a vital role in this reaction, which could tune carbocation reactivity through reversible C–I bond formation for controlling reaction selectivity, and a series of competitive reactions are completely eliminated in the presence of multiple reactivity pathways. The present dual catalytic protocol affords a very convenient method for direct synthesis of various difluoro-γ-lactams from simple and readily available starting materials under mild reaction conditions.

Visible light induced photoredox catalysis is an efficient method for radical activation. Herein, we report the photoredox catalysis involving an intramolecular radical–radical coupling reaction that proceeds through a biradical intermediate. This protocol represents a new synthetic route to construct multi-substituted N-heterocycles. Four, five and six-membered N-heterocyclic structures with a quaternary carbon center are accessible under mild conditions.

Oxazolo[3,2-a]indolone and spiro[furan-2,2′-indolin]one are synthesized by the visible-light-induced aerobic dearomative reaction of indoles. The common indole tethered alcohol at the N1 or C2 position reacts in a cascade fashion, providing facile access to diverse indolone scaffolds.

C-1-monofluoromethylated tetrahydroisoquinolines are obtained by visible-light photoredox-catalyzed reaction of tetrahydroisoquinolines with β-fluorinated gem-diols as CF-source under mild reaction conditions.