Tandem Radical Reactions of Carbon Monoxide, Isonitriles, and Other Reagent Equivalents of the Geminal Radical Acceptor/Radical Precursor Synthon

A silver catalyzed domino reaction of N-cyanamide alkenes and 1,3-dicarbonyls for the synthesis of quinazolinones

A silver catalyzed domino reaction of N-cyanamide alkenes and 1,3-dicarbonyls has been developed for the facile synthesis of quinazolinones.

Synthesis of pyridine trans-tetrafluoro-λ6-sulfane derivatives via radical addition

Pyridine-trans-SF₄-alkenes or -alkanes have been synthesized for the first time via the radical addition reactions of pyridine-trans-SF₄Cl to alkynes or alkenes in good to high yields.

A four-component radical cascade trifluoromethylation reaction of alkenes enabled by an electron-donor–acceptor complex

A four-component radical cascade trifluoromethylation of alkenes, enabled by an electron-donor–acceptor complex between Togni's reagent and Hantzsch ester, has been described.

A Copper-Catalyzed Aerobic [1,3]-Nitrogen Shift through Nitrogen-Radical 4-exo-trig Cyclization

A novel radical [1,3]-nitrogen shift catalyzed by copper diacetate under an oxygen atmosphere (1 atm) has been developed for the construction of a diverse range of indole derivatives from α,α-disubstituted benzylamine. In this reaction, oxygen was used as a clean terminal oxidant, and water was produced as the only by-product. Five inert bonds were cleaved, and two C-N bonds and one C-C double bond were constructed in one pot during this transformation. This unique method demonstrated broad application protential for the late-stage modification of biologically active natural products and drugs. Mechanistic investigations indicate that a unique 4-exo-trig cyclization of an aminyl radical onto a phenyl ring is involved in the catalytic cycle.

Bromoallylation of Alkenes Leading to 4-Alkenyl Bromides Based on Trapping of β-Bromoalkyl Radicals

A radical-chain addition of allyl bromides to aryl alkenes, vinyl ester, and vinyl phthalimide was studied in which elusive β-bromoalkyl radicals were trapped efficiently to give 5-bromo-1-pentenes in good to high yields (16 examples). A subsequent carbonylative radical cyclization with AIBN/Bu₃SnH/CO was successful in giving the corresponding 3,5-disubstituted cyclohexanone derivatives in moderate yields. Synthesis of a piperidine ring was also successful by subsequent reaction with primary amine.

Synthesis of 2-Amino-3-hydroxy-3H-indoles via Palladium-Catalyzed One-Pot Reaction of Isonitriles, Oxygen, and N-Tosylhydrazones Derived from 2-Acylanilines

A cyanide-free one-pot procedure was developed to access 2-amino-3-hydroxy-3H-indoles, which involved: (1) in situ formation of ketenimines by the reaction of N'-(1-(2-aminophenyl)ethylidene)-p-tosylhydrazones with isonitriles; (2) the intramolecular nucleophilic attack of ketenimines by the amino in phenyl furnishing the ring closure leading to 2-aminoindoles; (3) the oxidation of 2-aminoindoles by O₂ leading to 2-amino-3-hydroxy-3H-indoles. This strategy represents not only a key compliment to the sporadic synthetic methods toward 2-amino-3-hydroxy-3H-indoles but also progress in N-tosylhydrazone, isonitrile, and ketenimine chemistry.

Redox-Neutral Dual Functionalization of Electron-Deficient Alkenes

Visible‐light photoredox catalysis has been utilized in a new multicomponent reaction forming β‐functionalized δ‐diketones under mild conditions in an operationally convenient manner. Single‐electron reduction of in situ generated carboxylic acid derivatives forms acyl radicals that react further via 1,2‐acylalkylation of olefins in an intermolecular, three‐components cascade reaction, giving valuable synthetic entities from readily available starting materials. A diverse set of substrates has been used, demonstrating robust methodology with broad substrate scope.

PhI(OCOCF3)2-Mediated Construction of a 2-Spiropseudoindoxyl Skeleton via Cascade Annulation of 2-Sulfonamido-N-phenylpropiolamide Derivatives

A cascade annulation of 2-sulfonamido-N-phenylpropiolamide derivatives leading to the construction of the 2-spiropseudoindoxyl skeleton was realized under mild conditions with phenyliodine(III) bis(trifluoroacetate) (PIFA) as the sole oxidant. This metal-free spirocyclization process is suggested to encompass a sequential C(sp²)-C(sp) and C(sp²)-N bond formation with the concomitant introduction of a carbonyl oxygen.

Cu-catalyzed intermolecular oxyalkylation of styrenes under air: access to diverse iminolactones

A practical, simple, and efficient copper-catalyzed oxyalkylation of styrenes with α-bromoacetamides for the synthesis of iminolactones was developed under air.

ZnBr2-Mediated oxidative spiro-bromocyclization of propiolamide for the synthesis of 3-bromo-1-azaspiro[4.5]deca-3,6,9-triene-2,8-dione

ZnBr₂-Mediated oxidative ipso-bromocyclization of N-arylpropoilamide was utilized herein for the synthesis of 3-bromo-1-azaspiro[4.5]deca-3,6,9-triene-2,8-dione with high efficiency and a broad tolerance for functional groups.

Initiating radical reactions with non-thermal plasmas

Non-thermal plasmas initiate radical chain reactions under mild conditions without the need for any added initiators.

Visible-Light-Induced Trifluoromethylation of Isonitrile-Substituted Methylenecyclopropanes: Facile Access to 6-(Trifluoromethyl)-7,8-Dihydrobenzo[k]phenanthridine Derivatives

A new visible-light-induced trifluoromethylation of isonitrile-substituted methylenecyclopropanes is developed. A range of substituted 6-(trifluoromethyl)-7,8-dihydrobenzo[k]phenanthridine derivatives are readily furnished by this newly developed tandem reaction with moderate to good yields. This reaction allows the direct formation of two six-membered rings and three new C-C bonds, including the C-CF3 bond, under visible light irradiation.

Installing amino acids and peptides on N-heterocycles under visible-light assistance

Readily available natural α-amino acids are one of nature’s most attractive and versatile building blocks in synthesis of natural products and biomolecules. Peptides and N-heterocycles exhibit various biological and pharmaceutical functions. Conjugation of amino acids or peptides with N-heterocycles provides boundless potentiality for screening and discovery of diverse biologically active molecules. However, it is a great challenge to install amino acids or peptides on N-heterocycles through formation of carbon-carbon bonds under mild conditions. In this article, eighteen N-protected α-amino acids and three peptides were well assembled on phenanthridine derivatives via couplings of N-protected α-amino acid and peptide active esters with substituted 2-isocyanobiphenyls at room temperature under visible-light assistance. Furthermore, N-Boc-proline residue was successfully conjugated with oxindole derivatives using similar procedures. The simple protocol, mild reaction conditions, fast reaction, and high efficiency of this method make it an important strategy for synthesis of diverse molecules containing amino acid and peptide fragments.

Radical perfluoroalkylation – easy access to 2-perfluoroalkylindol-3-imines via electron catalysis

Arylisonitriles react with alkyl and perfluoroalkyl radicals to form 2-alkylated indole-3-iminesviatwo sequential additions to the isonitrile moiety followed by homolytic aromatic substitution.

Recent progress in imidoyl radical-involved reactions

This review discusses the recent progress in imidoyl radical-involved reactions including the synthesis of functionalized heterocycles, nitriles, imines, amines,etc.

Recent advances in catalytic decarboxylative acylation reactions via a radical process

This review highlights the recent advances in radical decarboxylative cross-coupling reactions of α-keto acids which provide powerful tools for C–C and C–X bond formations.

A novel domino cyclization for the stereoselective synthesis of indeno[2,1-c]pyran and cyclopenta[c]pyran derivatives

A novel bicyclization of 2-(2-(hydroxymethyl)-1-methylene-2,3-dihydro-1H-inden-2-yl)ethanol with aldehydes in the presence of 10 mol% BF3·OEt2 in dichloromethane at 0-25 °C affords the biologically relevant indeno[2,1-c]pyran scaffolds in good yields with high selectivity. Similarly the bicyclization of 2-(1-(hydroxymethyl)-2-methylenecyclopentyl)ethanol with aldehydes generates the corresponding cyclopenta[c]pyran derivatives under similar conditions. This method is very useful to produce hematoxylin and brazilin like scaffolds.

The electron is a catalyst

The electron is an efficient catalyst for conducting various types of radical cascade reaction that proceed by way of radical and radical ion intermediates. But because electrons are omnipresent, catalysis by electrons often passes unnoticed. In this Review, a simple analogy between acid/base catalysis and redox catalysis is presented. Conceptually, the electron is a catalyst in much the same way that a proton is a catalyst. The 'electron is a catalyst' paradigm unifies mechanistically an assortment of synthetic transformations that otherwise have little or no apparent relationship. Diverse radical cascades, including unimolecular radical substitution reactions (SRN1-type chemistry), base-promoted homolytic aromatic substitutions (BHAS), radical Heck-type reactions, radical cross-dehydrogenative couplings (CDC), direct arene trifluoromethylations and radical alkoxycarbonylations, can all be viewed as electron-catalysed reactions.

Synthesis and crystal structure of 2-isocyano-4-methylphenyl diphenylacetate: a rare case of an easily accessible odourless isocyanide

Acidic hydrogen containing 2-isocyano-4-methylphenyl diphenylacetate, C22H17NO2, (I), was synthesized by the base-promoted reaction between 5-methylbenzoxazole and diphenylacetyl chloride. Achiral (I) crystallizes in the chiral P212121 space group. The C[triple-bond]N bond length is 1.164 (2) Å and the angle between the OCO and 2-isocyano-4-methylphenyl planes is 69.10 (16)°. Molecules are linked via C=O...H(phenyl) and bifurcated N[triple-bond]C...H(phenyl)/N[triple-bond]C...H(methine) hydrogen bonds, forming one-dimensional arrays.