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A one-step method to convert nitroarenes into aryl sulfones under operationally simple, transition-metal-free conditions is described. A range of nitroarenes were reacted with sodium sulfinates and caesium carbonate in N , N ′-dimethylpropyleneurea to afford aryl sulfones in up to 83% yield. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Concise assembly of spirooxindoles is of great significance but a challenging task in modern organic synthesis. Described herein is an unusual base‐promoted [4+2] spiroannulation of rarely used isatin‐derived β‐silylcarbinols with o‐halogen aromatic ketones, which enables rapid and modular synthesis of six‐membered carbocyclic spirooxindoles in high yields with excellent functional group tolerance (> 50 examples). Mechanistic experiments revealed that this reaction involved a Peterson olefination, Michael addition and intramolecular C(sp3) arylation cascade. The variegated synthetic derivatization of target products and successful construction of bioactive molecules further illustrate the synthetic potential in spirooxindole‐related drug discovery. [ABSTRACT FROM AUTHOR]

Herein the one‐pot thioesterification and hydrothiolation of α, β‐unsaturated esters with aliphatic thiols was reported at room temperature. The mechanism was indirectly revealed which α, β‐unsaturated thioester was the intermediate. The advantages of this method included transition‐metal‐free, mild conditions, broad substrate scope and good functional group tolerance. On the other hand, the hydrothiolation of α, β‐unsaturated aliphatic esters at room temperature was also developed. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A novel visible‐light‐induced radical cascade 6‐endo cyclization of dienes (N‐(2‐vinylphenyl)acryl amides) is developed utilizing α‐carbonyl bromides as alkyl reagents. This approach affords an efficient way for synthesizing six‐membered benzo‐fused lactam derivatives with chemo‐ and regio‐selectivity and good functional group tolerance. Primary, secondary, and tertiary bromides are well‐compatible with this cascade cyclization reaction. [ABSTRACT FROM AUTHOR]

1-Iodoalkynes are one type of the most reactive and the most practical intermediates in organic synthesis. Here, some facile and efficient methods for the 1-iodination of terminal alkynes are developed using N-iodosuccinimide (NIS) as an iodination reagent and some inexpensive mild bases as catalysts. K2CO3 and 4-dimethylaminopyridine (DMAP) have been proven to be the most suitable inorganic and organic bases, succeeding in 17 examples with excellent yields (up to 99%). [ABSTRACT FROM AUTHOR]

Efficient transition‐metal‐free synthesis of benzo[b]azepines and oxindoles is achieved via a radical relay cascade strategy employing halogen atom transfer (XAT) for aryl radical generation followed by intramolecular hydrogen atom transfer (HAT). Optimization yielded moderate to substantial yields under visible light irradiation. Preliminary biological assessments revealed promising anti‐tumor activity for select compounds. This study underscores the potential of XAT‐mediated radical relay cascades in medicinal chemistry and anticancer drug discovery. [ABSTRACT FROM AUTHOR]

The beginning of photochemical reactions revolutionized synthetic chemistry through sustainable practices. This review explores cutting‐edge developments in leveraging light‐induced processes for generating cascaded C−C and C‐hetero bonds without catalysts. Significantly, catalyst‐free photoinduced methodologies have garnered considerable attention, especially in the creation of varied heterocyclic frameworks for drug design and the synthesis of natural products. The article delves into underlying mechanisms, addresses limitations, and evaluates various methodologies, emphasizing the potential of photocatalyst and transition metal‐free photochemical reactions to enhance sustainability. Divided into two sections, it covers recent strides in C−C and C‐heteroatom and multiple C‐heteroatom bond formation reactions. [ABSTRACT FROM AUTHOR]

This article discusses a new method for synthesizing halogenated heterocycles, which are important in medicinal, materials, and agricultural chemistry. The authors propose a base-mediated cyclization method that is simple, robust, and scalable, providing good to excellent yields of indoles, benzofurans, and benzothiophenes. The text provides a detailed description of the experimental procedures and characterization data for the synthesis of various compounds, including IR spectra, NMR spectra, and high-resolution mass spectra. This information can be useful for researchers studying organic synthesis and chemical characterization. [Extracted from the article]

The Zweifel olefination is a highly efficient and versatile method for constructing carbon-carbon double bonds in organic synthesis. It avoids the use of transition metals and has been applied in natural product synthesis and drug discovery. Recent progress in the field includes the use of new organometallic species, electrochemical and photocatalyzed reactions, and exploration of milder reaction conditions. However, further research is needed to develop less functional-group-sensitive reagents and investigate new strategies for generating alkenyl boron complexes. [Extracted from the article]

A tandem carbonyl reduction and hydrodefluorination of β‐trifluoromethyl enones with hydrosilanes under transition‐metal‐free conditions was developed for the synthesis of a variety of valuable gem‐difluorovinyl alcohols. The hydrosilane could act as both a reductive agent and a C(sp3)‐F bond‐breaking promoter under mild reaction conditions. Synthetically useful organofluorides, such as gem‐fluorophosphine alkene, gem‐difluorovinyl ketone, and fluorinated dihydrofuran derivatives could be readily constructed by further transformations of the obtained gem‐difluorovinyl alcohols. Moreover, the method features mild reaction conditions, operational simplicity, excellent functional group tolerance, and scalability. [ABSTRACT FROM AUTHOR]

Synthesis of heteroaryl ortho‐substituted anilines is hitherto challenging. Herein we report scope and limitation of method for annulation of 1‐(2‐nitroaryl)pyrroles and derivatives of 2‐aminobenzyl alcohol to afford ortho‐substituted pyrrolo[1,2‐a]quinoxalin‐4‐yl anilines. Reaction conditions contained elemental sulfur as promoter, while were tolerant of a wide range of aryl and heteroaryl amines. Our method would offer a feasible tactic to yield anilines steric bulk with ortho heterocyclic substituents. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A convenient approach for the construction of 2‐aminobenzothiazoles via I2‐catalyzed tandem cyclization reaction of amines and carbon disulfide has been developed. The present approach starts from simple and readily available starting materials, affording a series of 2‐aminobenzothiazoles in up to 89% yields under metal‐free conditions. In this work, C—H/N—H functionalization was achieved and multiple C‐hetero bonds were successfully constructed in one pot. [ABSTRACT FROM AUTHOR]

This article discusses the synthesis of 2,2'-bipyridines through dehydrogenative dimerization of pyridines using sodium dispersion. The authors developed a method that does not require the use of transition metals, making it advantageous for applications where the contamination of transition metals may cause problems. The reaction conditions are mild and the use of sodium dispersion is sustainable and user-friendly. The authors also explored the scope of the dimerization reaction and found that 4-substituted pyridines reacted selectively at the 2-position to afford the corresponding 2,2'-bipyridines. [Extracted from the article]

This document provides spectroscopic data and experimental procedures for the synthesis of various compounds, including triarylmethanes and 1,1-diarylalkanes. The compounds were synthesized using specific reactions and characterized using NMR and IR spectroscopy. The yields and physical properties of the compounds are also reported. The data presented in the document match the literature. The compounds mentioned include (methoxymethylene)dibenzene, 1-(methoxy(phenyl)methyl)-4-methylbenzene, 1-methoxy-4-(methoxy(phenyl)methyl)benzene, (4-(methoxy(phenyl)methyl)phenyl)(methyl)sulfane, 4-(methoxy(phenyl)methyl)-N,N-dimethylaniline, 4-(4-(methoxy(phenyl)methyl)phenyl)morpholine, 4-(methoxy(phenyl)methyl)-1,1'-biphenyl, 1-fluoro-4-(methoxy(phenyl)methyl)benzene, 1-chloro-4-(methoxy(phenyl)methyl)benzene, 1-(methoxy(phenyl)methyl)-4-(trifluoromethyl)benzene, 1-(methoxy(phenyl)methyl)-2-methylbenzene, 1-methoxy-2-(methoxy(phenyl)methyl)ben [Extracted from the article]

Molecular oxygen‐mediated C−H bond alkylation of cyclic aldimines has been reported, which avoids the use of transition metals and additional oxidants. This method allows straightforward access to a series of cyclic aldimine derivatives through a free radical course. Furthermore, this transformation features mild conditions, excellent yields and good functional group tolerance. [ABSTRACT FROM AUTHOR]

Photoinduced chemical transformations have become a promising aspect of organic synthesis. This review focuses on the recent advancements in harnessing photoinduced processes for the formation of carbon‐chalcogen (C−O, C−S, C−Se, and C−Te) bonds under catalyst‐free conditions. These pathways typically involve either a radical mechanism or the creation of electron‐donor‐acceptor (EDA) complexes. The review explores the intricacies of the underlying mechanisms, discusses limitations, and evaluates the applicability of various methodologies in this field. Notably, photocatalyst and transition metal‐free photochemical reactions offer effective alternatives to enhance sustainability in this research area. [ABSTRACT FROM AUTHOR]

Transition‐mental‐free multi‐component hydroxysulfenylation of styrenes with NH4SCN and water to from β‐hydroxysulfides is established. The reaction mechanism proceeded via a domino reaction after a radical addition to 2‐phenylimidazo[1,2‐a]pyridines. This approach features a wide substrate scope and functional group compatibility, providing 34 compounds in acceptable yields. [ABSTRACT FROM AUTHOR]

The increasing global warming concerns have propelled a surge in the demand for sustainable energy sources within the domain of synthetic organic chemistry. A particularly prominent area of research has been the development of mild synthetic strategies for generating heterocyclic compounds. Heterocyclic compounds containing boron have notably risen to prominence as pivotal reagents in a myriad of organic transformations, showcasing their wide‐ranging applicability. This comprehensive review is aimed at collecting the literature pertaining to borylation reactions induced by light, specifically focusing on photocatalyst‐free and transition metal‐free methodologies. The central emphasis is on delving into selective mechanistic investigations. The amalgamation and analysis of these research insights elucidate the substantial potential inherent in eco‐friendly approaches for synthesizing heterocyclic compounds, thus propelling the landscape of sustainable organic chemistry. [ABSTRACT FROM AUTHOR]

In the presence of cesium carbonate, ynones bearing an ortho‐amino group reacted with cyclic β‐ketoesters through conjugated addition/carbon‐carbon σ‐bond cleavage/nucleophilic aromatic substitution tandem reaction to obtain 4‐quinolones fused with medium‐sized rings in good yields. This is the first example of synthesis of 4‐quinolones through base‐promoted insertion reactions of carbon‐carbon triple bonds into carbon‐carbon σ‐bonds. Notable features of this program are mild and transition‐metal‐free reaction conditions. [ABSTRACT FROM AUTHOR]

A transition‐metal‐free one‐pot procedure for the difunctionalization of alkynes by C−C triple bond oxidation and transformation towards chromone derivatives has been developed. It involves cascade reactions for carbonylation of alkynes, base‐promoted C−C σ‐bond cleavage, and intramolecular cyclization. This procedure provides an efficient protocol for the synthesis of polysubstituted chromones from readily available starting materials. [ABSTRACT FROM AUTHOR]

It should be mentioned that so far electrocarboxylation has been mainly explored for the carboxylation of olefins and imines, and only a few reports have been published on direct electrocatalytic C(sp SP 3 sp )-H bond carboxylation reactions. In previous studies, transition-metal or transition-metal-free methodologies proceeded through C(sp SP 3 sp )-H bond carboxylation reactions via enolate chemistry to trap a CO SB 2 sb molecule in order to give carboxylation products. Recent Advances on the Carboxylations of C(sp3)-H Bonds Using CO2 as the Carbon Source Keywords: carbon dioxide; transition-metal; transition-metal-free; thermochemical strategy; visible-light-induced photocatalysis; electrocatalysis; reductive C-H carboxylations; carboxylic acids EN carbon dioxide transition-metal transition-metal-free thermochemical strategy visible-light-induced photocatalysis electrocatalysis reductive C-H carboxylations carboxylic acids 1327 1342 16 07/11/23 20230725 NES 230725 Graph 1 Introduction The carboxylic acid unit is omnipresent in bioactive drug molecules, pharmaceuticals, natural products, and agrochemicals. [Extracted from the article]

A multicomponent tandem arylation reaction was established under transition‐metal‐free conditions to synthesize structurally diverse imidazo[1,2‐a]pyridines. As N,N‐dimethylaniline is not only a reactant but also a methylation reagent, its use affords an alternative route for methylation. This approach features mild reaction conditions and good functional group tolerance, providing 29 compounds in acceptable yields. [ABSTRACT FROM AUTHOR]

An environmentally friendly oxidation system has proposed for the practical and scalable production of value‐added 2,5‐furandicarboxylic acid from 1 kg of 5‐hydroxymethylfurfural. The system is composed of a simple base, oxygen, and a green solvent, thereby providing a sustainable and economical approach to organic synthesis. To gain insight into the mechanism of this oxidation process, NMR spectroscopic analysis and kinetic study are used for the mechanistic investigation of this environmentally friendly oxidation process. [ABSTRACT FROM AUTHOR]

A direct strategy for the preparation of fused thienoindoles from substituted indoles and elemental sulfur has been reported. The present approach produces a range of structurally valuable fused thienoindoles in 51–78% yield under transition‐metal‐free conditions, which may have potential applications in pharmaceutical industry and organic functional materials. In this work, the double C−S bonds formation is achieved via base promoted direct sulfuration of C−H bonds with elemental sulfur. [ABSTRACT FROM AUTHOR]

Herein, an efficient lithium tert‐butoxide/DMSO‐mediated rapid synthesis of naphthalenes, benzofurans, and indoles is reported. The anticipated aromatics and heteroaromatics are obtained in high yields within a few minutes, even in a decagram‐scale reaction. [ABSTRACT FROM AUTHOR]

Use of sustainable energy sources in synthetic organic chemistry has become one of the most popular research topics due to environmental pollution and global warming. In this review, we discuss photocatalyst-free and transition-metal-free light-induced reactions for the construction of carbon–carbon (C–C) bonds. The reaction systems discussed here are C–C bond formation via carbene intermediates, radical intermediates, and miscellaneous reactions via cyclization. 1 Introduction 2 C–C Bond Formation via Carbene Intermediates 3 C–C Bond Formation via Radical Intermediates 4 Miscellaneous C–C Bond Formation via Cyclization 5 Conclusion [ABSTRACT FROM AUTHOR]

Quinazolines are a privileged class of nitrogen-containing heterocycles, widely present in a variety of natural products and synthetic chemicals with a broad spectrum of biological and medicinal activities. Owing to their pharmaceutical applications and promising biological value, a variety of synthetic methodologies have been reported for these scaffolds. From the perspective of green and sustainable chemistry, transition-metal-free synthesis provides an alternative method for accessing several biologically active heterocycles. In this review, we summarize the recent progress achieved in the transition-metal-free synthesis of quinazolines and we cover the literature from 2015 to 2022. This aspect is present alongside the advantages, limitations, mechanistic rationalization, and future perspectives associated with the synthetic methodologies. [ABSTRACT FROM AUTHOR]

Branched allylic sulfones are scaffolds widely distributed in bioactive molecules and organic functional materials. The synthesis of allylic sulfones has been developed, e.g., using the Tsuji-Prost reaction, hydrosulfonylation and radical addition reactions, yet the hydrosulfonylation of unactive 1,3-diene without transition metals has been rarely explored. Here we synthesized branched allylic sulfones by boron-catalysed highly regioselective hydrosulfonylation of 1,3-diene with sulfinic acid, without transition metal catalysts. Compared with the previous methods, the advantages include readily available starting materials without pre-treatment; cheap boron trifluoride etherate; simple operation and easy scaling-up; the reaction does not require dry conditions, an inert atmosphere or a water scavenger; and excellent atom economy and regioselectivity. [ABSTRACT FROM AUTHOR]

A general chemo-enzymatic approach to synthesize both enantioenriched trans-3-alkoxyamino-4-oxy-2-piperidones, which are important scaffold for various naturally occurring alkaloids, is reported. To this end, a selective transition-metal-free dual C−H oxidation of piperidines mediated by the TEMPO oxoammonium cation (TEMPO+) was used, followed by enzymatic resolution of the corresponding alkoxyamino-2-piperidones with Candida antarctica lipase (CAL-B), to yield the title compounds in high enantiomeric excess (ee). The absolute configuration of both enantioenriched compounds was determined using chemical correlation and circular dichroism (CD) spectroscopy. The former method highlights the oxidative ring contraction of the trans-alkoxyamine-2-piperidone ring into its corresponding 2-pyrrolidinone. [ABSTRACT FROM AUTHOR]

Organoboron compounds are versatile synthons in synthetic chemistry, materials science, and medicinal chemistry. The preparation of them often requires either reactive organometallic reagents or transition metals. In recent years, transition‐metal‐free borylation methodologies using radical chemistry for C−B bond formation have attracted much attention and developed rapidly, which circumvents the use of preformed organometallic reagents. Various successful approaches from different radical precursors (such as carboxylic acids, amines and alcohols, which are abundant in nature) through either thermochemical, photochemical or electrochemical pathways have been developed. Therefore, in this review, we hope to provide an overview of recent advances in the discovery, development, and mechanistic study of transition‐metal‐free radical borylation processes. [ABSTRACT FROM AUTHOR]

An easy two‐/three‐component selective thioetherification of KSAc for the synthesis of a series of symmetrical/unsymmetrical 4‐alkylthio‐3‐halo‐2(5H)‐furanones has been described. The reaction without any metal catalyst or additive is carried out in air atmosphere at room temperature for 5 h, only using potassium thioacetate as an odourless sulfur source and a base simultaneously. The broad substrate scope and high yield make it important for the studies on both constructing C−S bond based on non‐aryl Csp2−X bond and synthesizing new 2(5H)‐furanone functional molecules. [ABSTRACT FROM AUTHOR]

Sodium tert -butoxide promotes the efficient etherification of alcohols with aryl bromides at room temperature. This simple procedure has a broad substrate scope, providing a practical pathway to aryl alkyl ethers in good yields without the addition of any transition metal species. [ABSTRACT FROM AUTHOR]

An iodine‐catalyzed aerobic α‐hydroxylation reaction of β‐dicarbonyl compounds is established under transition‐metal‐free conditions. This synthetic approach is applicable to a broad variety of readily accessible acyclic and cyclic substrates bearing amide, ester, and/or ketone groups, and can be conveniently conducted on a gram scale. [ABSTRACT FROM AUTHOR]

The cascade sequential reaction of α‐keto acids, 1‐iodoalkynes, and alkyl halides are reported herein to synthesize tetra‐substituted vinyl iodides. It represents an efficient protocol to access a diverse range of tetra‐substituted vinyl iodides starting from simple materials in a one‐pot fashion, featuring mild reaction conditions, ease of operation, and broad substrate scope. [ABSTRACT FROM AUTHOR]

A base‐mediated protocol has been established for the N‐acetylation of anilines/amines at room temperature. Reaction utilizes acetonitrile as a solvent as well as a surrogate of the acetyl group. Apart from acetonitrile, trifluoroacetonitrile could also be utilized in the reaction. The advantages of the reactions are simple operation, transition‐metal‐free approach, short reaction time, high functional group tolerance, and gram‐scale synthesis, which show the reaction's utility. The developed strategy represents a valuable approach in synthetic organic chemistry. [ABSTRACT FROM AUTHOR]

Direct C–H bond functionalization is the most effective technique to construct C–X (X = C, N, O, S, etc.), which could simplify the conventional synthesis methods. Transition-metal-catalyzed C–H bond functionalization needs metal catalysts such as palladium, rhodium, iridium, cobalt, copper, etc., which is not conducive to its sustainable development. In recent years, C(sp³ )-H bond functionalization without transition metal catalyst has been studied increasingly. In the meantime, electrochemistry has become one of the most dynamic research fields in organic synthesis for the reason that it can substitute the traditional expensive and polluting metal salt oxidants (e.g. Cu2+, Ag+ salt) with current/electrons to act as a redox agent. So the applications of electrochemistry combined with transition-metal-free C(sp³ )-H bond functionalization to solve some long-standing challenges have gradually gotten more and more attention in recent years. In this review, the researches on transition-metal-free electrochemical-induced C(sp³ )-H bond functionalization from 2016 to now will be systematically presented and the future research hotspots and difficulties in this field will also be prospected. [ABSTRACT FROM AUTHOR]

Iodomethane is usually used as an electrophilic methylation reagent. Herein, we report its use as a C1 organocatalyst for the aerobic ortho-selective trifluoromethylation of pyridines in the absence of a transition metal. Trifluoroacetic acid (TFA) was employed as an inexpensive, readily available trifluoromethyl source. The reaction efficiently produced a variety of trifluoromethylation products, with good functional group compatibility. Pyridine-containing drug molecules could also be selectively trifluoromethylated for late-stage functionalizations. Mechanistic studies showed that iodomethane selectively reacted with the pyridine starting material, rather than the pyridine product, to generate the corresponding N-methylpyridinium iodide. The decarboxylation of trifluoroacetic acid produced a trifluoromethyl anion, which added to the methylpyridinium iodide, and the subsequent aerobic rearomatization led to the generation of the ortho-trifluoromethylated product. [ABSTRACT FROM AUTHOR]

A simple protocol of metal‐free C−H benzylation on the C3 position of quinoxalin‐2(1H)‐ones via the oxidation of Di‐tert‐butyl peroxide (DTBP) was developed. This environmentally friendly transformation showed high efficiency and well‐tolerated functionalization, providing the desired products in moderate to good yields. The radical mechanism was confirmed by control experiment as well. [ABSTRACT FROM AUTHOR]

An efficient and environmentally‐friendly method for carbon‐centered radical cyclization of olefins via visible light photoredox catalysis to afford pyrrolo[3,2‐c]‐quinolines, oxindoles and quinoline‐2,4‐diones is described. This novel reaction successfully activated the α C−H bonds in one‐carbon units such as esters, chlorinated hydrocarbons and cyano compounds via HAT (hydrogen atom transfer) process by means of aryldiazonium salts. The transformation features good functional group tolerance, broad substrate scope, high atom economy, no need for transition metal or high temperature. [ABSTRACT FROM AUTHOR]

In the presence of iodine, the synthesis of S‐benzoazolyl chromone derivatives by one‐pot manner is reported. Thus, 2‐aminophenol firstly reacted with tetramethylthiuram disulfide (TMTD) to form 2‐mercaptobenzoxazole, and then coupled with 2‐hydroxyphenyl enaminones to obtain S‐benzoazolyl chromones through one‐pot manner. This method features mild conditions, easy operation, environmentally friendliness and wide substrate scopes, illustrating practical application value in organic synthesis. [ABSTRACT FROM AUTHOR]

KOtBu mediates the reaction between 2‐amino arylcarbaldehydes and benzyl/alkyl cyanides toward the expeditious formation of 2‐aminoquinolines under transition‐metal‐free conditions. The described transformation proceeds through in‐situ generated enimine intermediate from benzyl/alkyl cyanides under KOtBu‐mediated reaction conditions. The substituted 2‐aminoquinolines were realized in excellent yields at room temperature and shorter reaction time. The designed process exhibits operational simplicity and broad functional group tolerance in delivering the products of high significance. [ABSTRACT FROM AUTHOR]

A green and general method for the direct transformation of aldehydes to nitriles was developed. This method features a broad scope of substrates including aromatic, heterocyclic, and aliphatic aldehydes, by using I2/NH4Br in aqueous ammonia. Readily available aldehydes can be smoothly converted to corresponding nitriles in one‐step under open air at room temperature for 1–12 hours. This protocol is transition‐metal‐free and could be applied for the synthesis of various key cyano (CN)‐containing molecules. [ABSTRACT FROM AUTHOR]

Ligand coupling on sulfur, as an alternative to transition-metal-catalyzed cross-coupling reactions, is a useful method for connecting sp2 carbons. Although pioneered more than 50 years ago, its synthetic utility has been overlooked until recently. This short review summarizes progress in C(sp2)–C(sp2) bond formation using ligand coupling on sulfur and discusses control of selectivity, expansion of the scope, and applications of the reaction. 1 Introduction 2 Cross-Coupling of Heteroaryl Reagents 3 Phenothiazinium-Mediated C(sp2)–C(sp2) Cross-Coupling 4 C(sp2)–C(sp2) Bond Formation Mediated by Sulfuranes Generated from Arynes and Sulfoxides 5 S -Alkenylbenzothiophenium-Mediated Alkenyl-Alkenyl Coupling 6 Conclusion [ABSTRACT FROM AUTHOR]

An efficient and transition metal‐free C(sp3)−H sulfonylation method is described for the synthesis of 2‐sulfolmethyl quinolines from 2‐methylquinolines and the inexpensive sulfonyl hydrazides. Generally, this protocol uses KI as an additive in the presence of the oxidant tert‐butyl peroxybenzoate (TBPB), an efficient and compatible benign method that delivers 2‐sulfolmethyl quinolines products in moderate to good yields. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A general transition‐metal‐free visible‐light‐promoted 3‐acetalation reaction of quinoxaline‐2(1H)‐ones was developed under mild conditions. By employing 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN) as an inexpensive photocatalyst, and glyoxylic acid acetal as a radical source, various acetalated quinoxaline‐2(1H)‐ones were constructed in moderate to good yields. Moreover, the versatility of this protocol is highlighted by the successful application in the late‐stage modification of drug molecules and the various functionality transformations. The excellent antitumor activity of the acetalated product demonstrated that this streamlined and sustainable approach could have emerged as a powerful strategy for structural modification in medicinal chemistry. [ABSTRACT FROM AUTHOR]

The construction of N‐heterocyclic compounds from lignin remains a great challenge due to the complex lignin structure and the involvement of multiple steps, including the cleavage of lignin C−O linkages and the formation of heterocyclic aromatic rings. Herein, the first example of KOH mediated sustainable synthesis of quinoxaline derivatives from lignin β‐O‐4 model compounds in a one‐pot fashion under transition‐metal‐free conditions has been achieved. Mechanistic studies suggested that this transformation includes highly coupled cascade steps of cleavage of C−O bonds, dehydrative condensation, sp3 C−H bond oxidative activation, and intramolecular dehydrative coupling reaction. With this protocol, a wide range of functionalized quinoxalines, including an important drug compound AG1295, were synthesized from lignin β‐O‐4 model compounds and β‐O‐4 polymer, showcasing the application potential of lignin in pharmaceutical synthesis. [ABSTRACT FROM AUTHOR]

Considerable advances have been made in the area of C−H functionalization in the last few decades. A number of approaches including both directed and nondirected strategies have been developed thus far. Among the various C−H functionalizations, C−H borylation is of special interest due to the wide applications of organoboron compounds. In this regard, various transition‐metal‐catalyzed regioselective strategies have been developed. However, the major concern regarding metal‐catalyzed C−H borylation procedures is the requirement of a precious metal as well as the contamination by metal precursors in the desired products, which limit the application of this process in large‐scale synthesis. Therefore, recent trends have involved the use of transition‐metal‐free systems. We summarize recent developments in transition‐metal‐free regioselective C−H borylation. We believe that this Review will help to increase interest in this field and stimulate further progress. [ABSTRACT FROM AUTHOR]

A novel base‐promoted and highly efficient strategy for preparation of trifluoromethyl‐containing tetrasubstituted olefin derivatives has been developed. The trifluoroacetyl amination of alkynes is realized by C−N cleavage of trifluoroacetamides without any transition‐metal catalysts. Readily accessible substrates, good functional group tolerance and atom economy make this approach attractive for the synthesis of trifluoromethyl‐containing tetrasubstituted olefins. [ABSTRACT FROM AUTHOR]