Cu0-Promoted Truce-Smiles Rearrangement for Aryl-Difluoromethylenation of C═C Bonds via a Reductive Radical-Polar Crossover Process

An efficient Cu0-promoted Truce-Smiles rearrangement for the aryl-difluoromethylenation of C═C bonds by the reaction of N-alkyl-N-(arylsulfonyl)methacrylamide and 2-bromodifluoromethyl-1,3-benzodiazole via a reductive radical-polar crossover process under mild reaction conditions is presented. The protocol enables practical access to a variety of single regioisomer α-aryl-β-difluoromethylene amides in good to excellent yields through consecutive difluoromethylenation, radical-polar crossover, 1,4-aryl migration, SO2 extrusion, and N-H bond formation cascade reaction.

Copper-Catalyzed Trifunctionalization of Heteroaryl-Substituted 1-Hexenes via Remote Heteroaryl Migration

A copper-catalyzed trifunctionalization (trifluoromethylation, heteroarylation, and cyanation) of heteroaryl-substituted 1-hexenes via remote heteroaryl migration is reported. A variety of CF3 and heteroaryl-containing nitriles were readily constructed under mild conditions. The reaction features high chemo- and regioselectivities and represents a convenient method for the synthesis of multifunctionalized molecules in organic synthesis.

Recent Advances in Photochemical Asymmetric Three-Component Reactions

Over the past decades, asymmetric photochemical synthesis has garnered significant attention for its sustainability and unique ability to generate enantio-enriched molecules through distinct reaction pathways. Photochemical asymmetric three-component reactions have demonstrated significant potential for the rapid construction of chiral compounds with molecular diversity and complexity. However, noteworthy challenges persist, including the participation of high-energy intermediates such as radical species, difficulties in precise control of stereoselectivity, and the presence of competing background and side reactions. Recent breakthroughs have led to the development of sophisticated strategies in this field. This review explores the intricate mechanisms, synthetic applications, and limitations of these methods. We anticipate that it will contribute towards advancing asymmetric catalysis, photochemical synthesis, and green chemistry.

Accessing chiral sulfones bearing quaternary carbon stereocenters via photoinduced radical sulfur dioxide insertion and Truce-Smiles rearrangement

From the viewpoint of synthetic accessibility and functional group compatibility, photoredox-catalyzed sulfur dioxide insertion strategy enables in situ generation of functionalized sulfonyl radicals from easily accessible starting materials under mild conditions, thereby conferring broader application potential. Here we present two complementary photoinduced sulfur dioxide insertion systems to trigger radical asymmetric Truce-Smiles rearrangements for preparing a variety of chiral sulfones that bear a quaternary carbon stereocenter. This protocol features broad substrate scope and excellent stereospecificity. Aside from scalability, the introduction of a quaternary carbon stereocenter at position β to bioactive molecule-derived sulfones further demonstrates the practicality and potential of this methodology.

Recent Advances in 1,2-Amino(hetero)arylation of Alkenes

Alkene amino(hetero)arylation presents a highly efficient and straightforward strategy for direct installation of amino groups and heteroaryl rings across a double bond simultaneously. An extensive array of practical transformations has been developed via alkene difunctionalization approach to access a broad range of medicinally valuable (hetero)arylethylamine motifs. This review presents recent progress in 1,2-amino(hetero)arylation of alkenes organized in three different modes. First, intramolecular transformations employing C, N-tethered alkenes will be introduced. Next, two-component reactions will be discussed with different combination of precursors, N-tethered alkenes and external aryl precursor, C-tethered alkenes and external amine precursor, or C, N-tethered reagents, and alkenes. Last, three-component intermolecular amino(hetero)arylation reactions will be covered.

Palladium-catalyzed oxidative Heck reaction of non-activated alkenes directed by fluorinated alcohol

A new reactivity pattern for the regio- and stereoselective oxidative arylation of non-activated alkenes by introducing a trifluoromethyl group in the substrate enol has been established.

Radical-mediated rearrangements: past, present, and future

Rearrangement reactions, one of the most significant transformations in organic chemistry, play an irreplaceable role in improving synthetic efficiency and molecular complexity. Concomitant cleavage and reconstruction of chemical bonds can display the great artistry and the glamour of synthetic chemistry. Over the past century, ionic rearrangement reactions, in particular those involving cationic pathways, have represented most of the research. Alongside the renaissance of radical chemistry, radical-mediated rearrangements have recently seen a rapid increase of attention from the chemical community. Many new radical rearrangements that extensively reveal the migratory behaviour of functional groups have been unveiled in the last decade. This Review provides a comprehensive perspective on the area from the past to present achievements, and brings up the prospects that may inspire colleagues to develop more useful synthetic tools based on radical rearrangements.

Radical Aryl Migration from Boron to Carbon

Radical aryl migration reactions represent a unique type of organic transformations that involve the intramolecular migration of an aryl group from a carbon or heteroatom to a C- or heteroatom-centered radical through a spirocyclic intermediate. Various elements, including N, O, Si, P, S, Sn, Ge, and Se, have been reported to participate in radical aryl migrations. However, radical aryl migration from a boron center has not been reported to date. In this communication, radical 1,5-aryl migration from boron to carbon in aryl boronate complexes is presented. C-radicals readily generated through radical addition onto alkenyl aryl boronate complexes are shown to engage in 1,5-aryl migration reactions to provide 4-aryl-alkylboronic esters. As boronate complexes can be generated in situ by the reaction of alkenylboronic acid esters with aryl lithium reagents, the aryl moiety is readily varied, providing access to a series of arylated products starting from the same alkenylboronic acid ester via divergent chemistry. Reactions proceed with high diastereoselectivity under mild conditions, and also the analogous 1,4-aryl shifts are feasible. The suggested mechanism is supported by DFT calculations.

Oxidative alkylation/alkynylation of terminal alkenes via alkylaldehyde decarbonylation and 1,2-alkynyl migration

A metal-free oxidative alkene alkylation/alkynylation of 1,4-enyn-3-ols with alkylaldehydes has been achieved, which offers a general access to the challenging quaternary carbon-containing but-3-yn-1-ones. The method features excellent functional group tolerance, broad substrate scope and exquisite selectivity, and provides a strategy for the difunctionalization of functional alkenes and utilization of alkylaldehydes as alkylating reagents through decarbonylation and 1,2-alkynyl migration.

Copper-catalyzed enantioselective synthesis of bridged bicyclic ketals from 1,1-disubstituted-4-methylene-1,6-hexanediols and related alkenols

Bridged bicyclic ketals display a range of bioactivities. Their catalytic enantioselective synthesis from acyclic 1,1-disubstituted alkene diols is disclosed. This reaction combines asymmetric catalysis with a distal radical migration. Alkynes and arenes undergo the group transfer.

Recent advances in 1,4-functional group migration-mediated radical fluoroalkylation of alkenes and alkynes

Recently, the combination of radical fluoroalkylation of alkenyl or alkynyl moieties and 1,4-functional group migration (1,4-FGM) has emerged as a powerful strategy for the synthesis of fluorine-containing compounds. In this article, some representative reactions of 1,4-FGM-mediated radical fluoroalkylation of N-(arylsulfonyl)acrylamides, tertiary alcohol-containing alkynes, tertiary alcohol-containing alkenes and intermolecular 1,4-FGM-type substrates have been discussed based on the types of substrates.

Iron-catalyzed three-component intermolecular trifluoromethyl-acyloxylation of styrenes with NaSO2CF3 and benzoic acids

A new iron-catalyzed intermolecular three-component trifluoromethyl-acyloxylation of styrenes has been developed with a broad substrate scope under mild conditions.

Photoredox-Catalyzed Remote Difunctionalizations of Alkenes To Synthesize Fluoroalkyl Ketones with Dimethyl Sulfoxide as the Oxidant

Visible light-mediated cascade remote oxyfluoroalkylation of alkenes under mild conditions is developed for the first time. The key point of this transformation is the incorporation of alkene fluoroalkylation-initiated remote benzyl C-H bond activation via a 1,5-H shift in a highly controlled site-selective manner and Kornblum reaction with dimethyl sulfoxide as the oxidant. With this method, a broad array of fluoroalkyl groups were introduced into a double bond to produce 1,6-fluoroalkylated ketones at room temperature.

Copper-catalyzed three-component reaction of N-heteroaryl aldehydes, nitriles, and water

An efficient and straightforward method for the synthesis of N-heteroaroyl imides has been successfully developed involving a copper-catalyzed radical-triggered three-component reaction of N-heteroaryl aldehydes, nitriles, and water. Mechanistic studies indicate that the reaction may undergo a radical-triggered Ritter-type reaction in which water serves as the oxygen source for the formation of the C-O bond. The reaction has advantages such as a broad substrate scope for the N-heteroaryl aldehydes, atom economy, and simple operation.

Perfluoroalkylative pyridylation of alkenes via 4-cyanopyridine-boryl radicals

A metal- and photo-free method for the perfluoroalkylative pyridylation of alkenes has been developed.

A metal-free and photo-free method for the perfluoroalkylative pyridylation of alkenes has been developed via a combination of computational and experimental studies. Density functional theory calculations and control experiments indicate that the homolysis of R_f–X (X = Br, I) bonds by the 4-cyanopyridine-boryl radicals in situ generated from 4-cyanopyridine and B₂pin₂ is the key step. Sequential addition of R_f radicals to alkenes and the selective cross-coupling of the resulting alkyl radicals and 4-cyanopyridine-boryl radicals gives alkene difunctionalization products with a quaternary carbon center. This method exhibits a broad substrate scope and good functional group compatibility.

Photoinitiated Three-Component α-Perfluoroalkyl-β-heteroarylation of Unactivated Alkenes via Electron Catalysis

A visible-light-initiated α-perfluoroalkyl-β-heteroarylation of various alkenes with perfluoroalkyl iodides and quinoxalin-2(1 H)-ones is presented. This three-component radical cascade reaction allows an efficient synthesis of a range of perfluoroalkyl containing quinoxalin-2(1 H)-one derivatives in moderate to excellent yields under mild conditions. Reactions proceed via acidic aminyl radicals that are readily deprotonated to give the corresponding radical anions able to sustain the radical chain as single electron transfer reducing reagents. Hence, the overall cascade classifies as an electron-catalyzed process.

Cleavage of carbon–carbon bonds by radical reactions

This review provides insights into the in situ generated radicals triggered carbon–carbon bond cleavage reactions.

Intermolecular, redox-neutral azidoarylation of alkenes via photoredox catalysis

An intermolecular, redox-neutral azidoarylation of alkenes with pyridines and TMSN₃ has been reported via visible light-induced photoredox catalysis.

Metal-free, intermolecular carbopyridylation of alkenes via visible-light-induced reductive radical coupling

An efficient, metal-free strategy for the intermolecular three-component carbopyridylation of styrenes, enabled by Hantzsch ester and visible light, has been described.

An efficient, metal-free strategy for the intermolecular three-component carbopyridylation of styrenes, enabled by Hantzsch ester and visible light, has been described. This versatile protocol gives access to important β-CF₃ pyridines, through the regioselective, sequential formation of two C–C bonds without the use of exogenous catalysts. The value of this benign protocol has been demonstrated through functionalizations of natural-product- and drug-based complex molecules.

Synthesis of CF3CH2-Containing Indolines by Transition-Metal-Free Aryltrifluoromethylation of Unactivated Alkenes

With an unactivated double bond as the radical acceptor, allyl amines underwent a metal-free trifluoromethylation/cyclization cascade with CF₃SO₂Na (Langlois' reagent), affording CF₃CH₂-containing indolines and tetrahydroisoquinolines, whose practical syntheses are significant challenges. This protocol features mild conditions, low cost, and a broad substrate scope.

TEMPO promoted direct multi-functionalization of terminal alkynes with 2-oxindoles/benzofuran-2(3H)-one

Highly selective and catalyst-free tandem multi-functionalization of terminal alkynes was developed with 2-oxindoles and benzo-furan-2(3H)-one using TEMPO both as a radical promoter and a trapping reagent. This work expands the scope of the radical-cascade addition/trapping process of alkynes for the effective construction of various β-oxyl carbonyls in moderate to good yields.

Distal radical migration strategy: an emerging synthetic means

In the past three years, we have witnessed the rapid development of C–C and C–H bond functionalization by means of long-distance radical migration events which bring us a new platform to deal with the challenging C–C and C–H bond functionalization.