Palladium-Catalyzed Three-Component Tandem Coupling–Carboannulation Reaction Leading to Polysubstituted [60]Fullerene-Fused Cyclopentanes

Copper-Mediated Radical-Induced Ring-Opening Relay Cascade Carboannulation Reaction of [60]Fullerene with Cyclobutanone Oxime Esters: Access to [60]Fullerene-Fused Cyclopentanes

An unexpected copper-mediated radical-induced ring-opening relay cascade carboannulation reaction of [60]fullerene with cyclobutanone oxime esters is presented for the preparation of various Cl-/Br-incorporated [60]fullerene-fused cyclopentanes. The unique relay cascade transformation uses inexpensive copper salts as promoters and halogen sources and features simple redox-neutral conditions and a broad substrate scope, providing a practical access to a class of novel five-membered carbocycle-fused fullerenes.

Stereoselective Synthesis of Substituted (Z)-N-Allyl Sulfonamides via a Palladium-Catalyzed Three-Component Tandem Reaction

This paper reports the efficient synthesis of substituted (Z)-N-allyl sulfonamides via a palladium-catalyzed three-component tandem reaction of N-buta-2,3-dienyl sulfonamides with iodides and sulfonyl hydrazide or sulfinic acid sodium salt as nucleophiles. Pd(PPh₃)₄ (2.5 mol %), K₂CO₃, and THF were used as the optimal catalyst, base, and solvent, respectively. The substituted (Z)-N-allyl sulfonamides were obtained in a 30-83% overall yield. Mechanistic investigations revealed that the formation of the single (Z)-isomer was controlled by the formation of a six-membered palladacycle intermediate.

[60]Fullerene-Fused Cyclopentanes: Mechanosynthesis and Photovoltaic Application

The mechanochemical cascade reaction of [60]fullerene with 3-benzylidene succinimides, diethyl 2-benzylidene succinate, or 2-benzylidene succinonitrile in the presence of an inorganic base has been investigated under solvent-free and ball-milling conditions. This protocol provides an expedient method to afford various [60]fullerene-fused cyclopentanes, showing advantages of good substrate scope, short reaction time, and solvent-free and ambient reaction conditions. Furthermore, representative fullerene products have been applied in inverted planar perovskite solar cells as efficient cathode interlayers.

KOtBu-Promoted, Three-Component Domino Reaction of Arenes(indoles/phenols), C60, and (Per/poly)fluoroarenes: Achieving Direct C-C Cross-Coupling of Fullerene with (Per/poly)fluoroarenes

A KO^tBu-promoted, three-component cross-coupling of arenes(indoles/phenols), C₆₀, and (per/poly)fluoroarenes has been established for the one-pot efficient synthesis of various 1,4-arene-bridged bis(polyfluoroaryl)-functionalized [60]fullerenes. This developed reaction system demonstrates good functional group compatibilities with broad substrate scope, which exhibits high regio- and chemoselectivities. Further control experiment succeeded in providing a one-pot protocol for the synthesis of various 1,2-N-(per/poly)fluoroarene-substituted 1,2-(3-indole)(hydro)fullerenes.

Transition-Metal-Free Domino Reaction of [60]Fullerene, Indole, and DMSO/HCl: One-Pot Access to Diverse N-Substituted [60]Fulleroindole Derivatives

An unprecedented multicomponent domino reaction of [60]fullerene, indole, and DMSO/HCl has been developed for the one-pot efficient synthesis of diverse N-substituted [60]fulleroindole derivatives. This methodology features simple operation, low cost, and transition-metal-circumvented and good functional group tolerance in indole.

Miscellaneous Passerini Reaction for α-Acyloxy Carboxamide: Synthesis and Process Optimization Study

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An accelerating effect of “Phase Transfer Catalyst” as additive was exposed for the Passerini three-component reactions and the influence on the reaction rate was studied concerning direct involvement of reactant molecules. The most flexible reaction for the rapid formation of diverse “α-acyloxycarboxamides” using passerini reaction involved multicomponent reactions using miscellaneous 2-(prop-2-ynyloxy)benzaldehyde with various aromatic acid and slightly non-polar fragment i.e. 2-isocyano-2,3,3-trimethylbutane and the representative molecule was characterized with resepct to DEPT135 NMR technique.

Palladium-Catalyzed Three-Component 1,4-Alkoxyarylation Reaction of [60]Fullerene

The palladium-catalyzed three-component alkoxyarylation reaction of [60]fullerene with primary/secondary alcohols and aryl iodides generates a series of 1,4-(alkoxy)(aryl)[60]fullerene derivatives. Plausible reaction pathways for the formation of 1,4-(alkoxy)(aryl)[60]fullerenes are proposed. In addition, the electrochemical properties of the synthesized 1,4-alkoxyarylation adducts are investigated.

Palladium-catalyzed decarboxylative [2 + 3] cyclocarbonylation reactions of [60]fullerene: selective synthesis of [60]fullerene-fused 3-vinylcyclopentan-4-ones and cyclopentane-4-carbaldehydes

A new palladium-catalyzed decarboxylative strategy has been developed toward direct cyclocarbonylation of [60]fullerene, selectively furnishing novel [60]fullerene-fused 3-vinylcyclopentan-4-ones and cyclopentane-4-carbaldehydes.

Attaching a Dipeptide to Fullerene as an Antioxidant Hybrid against DNA Oxidation

Emerging evidence has revealed that oxidative damages of DNA correlate with the pathogenesis of some diseases, and numerous investigations have also suggested that supplementation of antioxidants is beneficial for keeping health by rectifying in vivo redox status. Here, we construct antioxidative dipeptides with the Ugi four-component reaction (comprising p-aminobenzyl alcohol, benzaldehyde, or vanillin, a series of antioxidative carboxylic acids and isocyanides as reagents) and then attempt to attach the dipeptides to [60]fullerene by the Bingel reaction. However, this endeavor does not lead to the amelioration of the radical-scavenging property because abilities of fullerenyl dipeptides to trap 2,2'-diphenyl-1-picrylhydrazyl and galvinoxyl radicals are still dependent upon the phenolic hydroxyl group in the dipeptide scaffold rather than upon the fullerenyl group. Alternatively, when the obtained fullerenyl dipeptides are evaluated in a peroxyl radical-induced oxidation of DNA, it is found that introducing a fullerene moiety into dipeptide enables antioxidative effect to be enhanced 20-30% because the fullerene moiety facilitates the corresponding dipeptide to intercalate with DNA strands, and thus, to increase the antioxidative efficacy. Our results suggest that connecting an antioxidative skeleton with the hydrophobic fullerene moiety might lead to a series of novel antioxidant hybrids applied for the inhibition of DNA oxidation.

Palladium-Catalyzed Three-Component Coupling Reaction via Benzylpalladium Intermediate

Transition-metal catalyzed multi-component reactions have captured the attention of researchers in organic synthesis and drug synthesis due to their advantages of simple operation, easy availability of raw materials and without separation of intermediates. Among the multi-component reactions, the three-component processes have been developed into effective organic procedures. This personal account reviews our and other group's studies on the development of three-component coupling reaction for the rapid construction of two new chemical bonds simultaneously via benzylpalladium intermediates. Catalyst-switched three-component reactions of benzyl halides, activated olefins, and allyltributylstannane were successfully conducted to produce the corresponding benzylallylation products. Activation and conversion of carbon monoxide and carbon dioxide via π-benzylpalladium intermediates provide access to a wide range of unsaturated ketones and esters with excellent functional group tolerance. Meanwhile, other methods to produce benzylpalladium intermediates, including Heck insertion of alkenes into arylpalladium complexes, the oxidative addition of benzyl carbonate to palladium complexes and palladium-carbene migratory insertion, were also highlighted.

Metal-Free-Catalyzed Three-Component [2+2+2] Annulation Reaction of [60]Fullerene, Ketones, and Indoles: Access to Diverse [60]Fullerene-Fused 1,2-Tetrahydrocarbazoles

The first example of metal-free-catalyzed multicomponent annulation reaction of [60]fullerene has been developed for concise and efficient construction of novel [60]fullerene-fused 1,2-tetrahydrocarbazoles. Using inexpensive and readily available I₂ as a catalyst, [60]fullerene, ketones, and indoles undergo a formal [2+2+2] annulation process to conveniently assemble diverse 1,2-tetrahydrocarbazoles. Mechanistic studies indicate that this reaction proceeds through I₂-promoted generation of a 3-vinylindole structure with the characteristics of a conjugated diene followed by cycloaddition to [60]fullerene.

An "Umpolung Relay" Strategy: One-Pot, Twice Polarity Inversion Cascade Synthesis of Diversified [60]Fulleroindoles

An "umpolung relay" strategy, which includes an one-pot, twice polarity inversion cascade of C₆₀ via carbanion and carbocation polarity reversed relay pathway, has been developed for the synthesis of a diverse range of novel [60]fulleroindole derivatives.

One-pot, three-component regioselective coupling reaction of triphenylamine/carbazole derivatives with [60]fullerene and indoles via an “umpolung relay” strategy

An “umpolung relay” three-component regioselective coupling reaction of triphenylamine/carbazole derivatives with C60 and indoles was developed, which features high regioselectivity, broad substrate scope, and excellent functional group tolerance.

Facile access to amino-substituted cyclopentafullerenes: novel reaction of [60]fullerene with β-substituted propionaldehydes and secondary amines in the absence/presence of magnesium perchlorate

A series of scarce amino-substituted cyclopentafullerenes instead of the expected N-alkyl-2,5-disubstituted fulleropyrrolidines were synthesized in moderate to excellent yields via the simple one-step reaction of [60]fullerene with cheap and easily available β-substituted propionaldehydes and secondary amines in the absence/presence of magnesium perchlorate. The in situ generation of allylic amines from β-substituted propionaldehydes and secondary amines played a crucial role in the successful preparation of amino-substituted cyclopentafullerenes without additional carbons. With the addition of magnesium perchlorate, secondary amines containing ethyl group(s) could produce novel amino-substituted cyclopentafullerenes with two additional carbons. All the obtained cyclopentafullerenes displayed high stereoselectivity with cis isomers as the exclusive or major products. Plausible reaction mechanisms are proposed to elucidate the above-mentioned reaction process.

Iron-Catalyzed Redox-Neutral Radical Cascade Reaction of [60]Fullerene with γ,δ-Unsaturated Oxime Esters: Preparation of Free (N-H) Pyrrolidino[2',3':1,2]fullerenes

Herein an unprecedented iron(II)-catalyzed redox-neutral radical cascade reaction of [60]fullerene with γ,δ-unsaturated oxime esters is reported for the preparation of novel free (N-H) pyrrolidino[2',3':1,2]fullerenes. The transformation undergoes an intramolecular cyclization/intermolecular cyclization/oxidation/hydrolysis cascade, and features simple operation, broad substrate scope/high functional group compatibility as well as suitable for scale-up synthesis, providing a facile and practical access to a range of free pyrrolidino[2',3':1,2]fullerenes.

Palladium-Catalyzed Three-Component Coupling of Ynamides

A palladium-catalyzed regioselective three-component coupling of ynamides was developed. The reaction proceeded smoothly to furnish the desired products when carried out at 70 °C in acetonitrile/water with potassium carbonate in the presence of 2.5 mol % Pd₂(dba)₃·CHCl₃ without a ligand. Various iodides and boronic acids were used in this reaction, and a carbon-carbon bond was formed with satisfactory regioselectivity from the ynamides.

Alternative Access to Cyclopentafullerenes through the Reaction of [60]Fullerene with Aldehydes and Secondary Amines

A series of cyclopentafullerenes have been synthesized in high stereoselectivity by the thermal reaction of [60]fullerene with aldehydes and secondary amines. Both α,β-unsaturated aldehydes and saturated aldehydes can be utilized to synthesize cyclopentafullerenes as the cis isomers. The possible reaction mechanisms for the formation of cyclopentafullerenes are proposed on the basis of the experimental results.

Synthesis of [60]fullerene-fused dihydrobenzooxazepinesviathe palladium-catalyzed oxime-directed C–H bond activation and subsequent electrochemical functionalization

The palladium-catalyzed heteroannulation of [60]fullerene with oximes affords the unprecedented seven-membered [60]fullerene-fused dihydrobenzooxazepines, which can be further derivatized electrochemically.

Palladium-catalyzed synthesis of [60]fullerene-fused furochromenones and further electrochemical functionalization

The palladium-catalyzed heteroannulation of [60]fullerene with 4-hydroxycoumarins affords [60]fullerene-fused furochromenones, which can be further derivatized via an electrochemical method to synthesize 1,2,3,4-adducts.