Metal-free catalyzed synthesis of the (E)-vinyl sulfones via aromatic olefins with arylsulfonyl hydrazides

Synthesis of vinyl sulfones from aromatic olefins and arylsulfonyl hydrazides via I₂-TBHP catalyzed system under the N₂ atmosphere is described. Owing to no use of metal, only producing N₂ and water as the byproducts and directly available reactants, this reaction could validly avoid many disadvantages of the transition metal catalysts. In addition, the desired product can be collected with moderate to excellent yields under the suitable conditions.     

TFA-catalysed tandem double cyclisation: A one-pot,metal-free routes for novel indolo-imidazo[1,2-a]pyridine derivatives

A transition-metal free, one-pot tandem synthetic routes for novel indole and imidazo[1,2-a]pyridine derivative hybrids have been established. An efficient three-component reaction was designed with incorporation of two sequential Groebke–Blackburn–Bienayme (GBB) and cyclization reaction in one-pot under mild acidic condition. The salient feature of this protocol is atom economy, good yield and operational simplicity. A molecular prospective library of 32 compounds was synthesized by utilizing the various substituted aryl aldehydes and 2-aminopyridine.     

Metal-free synthesis of 1,2,3-benzotriazines

The recent molecular iodine catalyzed [1,2]-rearrangement of aryl amines and 3-amino-1H-indazolesfor the synthesis of 1,2,3-benzotriazines is highlighted.     

Metal-free synthesis of 1,2,3-benzotriazines

The recent molecular iodine catalyzed [1,2]-rearrangement of aryl amines and 3-amino-1H-indazolesfor the synthesis of 1,2,3-benzotriazines is highlighted.     

Metal-free synthesis of novel indolizines from chromones and pyridinium salts via 1,3-dipolar cycloaddition,ring-opening and aromatization

A simple, efficient, and economical synthetic approach to construct a variety of stucturally novel indolizines bearing a phenolic hydroxy group has been developed through 1,3-dipolar cycloaddition of chromones and pyridinium salts. The methodology is tolerant of a wide range of functional groups and applicable to library synthesis.     

Regioselective single-step synthesis of 2-aminoimidazole derivatives

A convenient single-step strategy for the regioselective assembly of 2-aminoimidazole derivatives is herein described. Through a transition metal-free domino addition/cyclization process, the reactions of unsymmetrical carbodiimides with propargylic amines mediated by Cs₂CO₃ selectively afforded the corresponding polysubstituted 2-aminoimidazoles in moderate to good yields under very mild conditions. The regioselectivity was reversed in the presence of TEA at a higher temperature. The obtained 2-(o-iodoaryl)amino imidazoles could be easily converted to 2-(2-biphenyl)amino imidazole, 2-(o-alkynylphenyl)amino imidazole, benzoimidazo[1,2-a]imidazole and N-(imidazol-2-yl)indole derivatives.     

CuI/Cu(OTf)2/DMSO system-catalyzed intramolecular oxidative cyclization of (o-alkynyl)arylketones: Efficient synthesis of 1,4-naphthoquinones

A concise and efficient method for the synthesis of 1,4-naphthoquinones has been successfully developed involving a CuI/Cu(OTf)₂/DMSO system-catalyzed intramolecular oxidative cyclization of (o-alkynyl)arylketones. The present protocol provided a novel approach to access functionalized 1,4-naphthoquinones from non-naphthoquinone precursors with good selectivity and functional group tolerance.     

Metal-free S-methylation of diaryl disulfides with di-tert-butyl peroxide

An efficient approach for S-methylation of diaryl disulfides with di-tert-butyl peroxide under metal-free and neutral conditions was established. The present protocol shows good functional group tolerance to afford aryl methyl sulfides in moderate to good yields.     

Synthesis of novel 5-substituted isophthalates from vinamidinium salts

Novel 5-substituted isophthalates were synthesized from the reaction of 2-substituted 1,3-bis(dimethylamino)-trimethinium salts with 1,3-bis(alkoxycarbonyl)acetone derivatives in the presence of sodium methoxide in ethanol at reflux.     

One-pot synthesis of 2-(quinoxalin-2-yl)benzoate through NBS-mediated sequential reaction of 2-alkynylbenozate and aryl-1,2-diamine

A metal-free route involving a sequential reaction of 2-alknylbenzoate and aryl-1,2-diamine is described for the generation of 2-(quinoxalin-2-yl)benzoate. The sequential reaction combines NBS-mediated diketonization of 2-alknylbenzoate and condensation reaction with aryl-1,2-diamine, and proceeds smoothly under mild reaction conditions and an array of 2-(quinoxalin-2-yl)benzoate is achieved with high efficiency and excellent functional group tolerance. Mechanism studies indicate oxygen transfer reaction is observed and water is incorporated into neighboring ester group.     

Stereocontrolled synthesis of bicyclic ureas and sulfamides via Pd-catalyzed alkene carboamination reactions

The synthesis of bicyclic ureas and sulfamides via palladium-catalyzed alkene carboamination reactions between aryl/alkenyl halides/triflates and alkenes bearing pendant cyclic sulfamides and ureas is described. The substrates for these reactions are generated in 3–5 steps from commercially available materials, and products are obtained in good yield with up to >20:1 diastereoselectivity. The stereochemical outcome of the sulfamide alkene addition is consistent with a mechanism involving anti-aminopalladation of the alkene, whereas the stereochemical outcome of the urea alkene addition is consistent with a syn-aminopalladation mechanism.     

A novel synthesis of 3-hydroxypiperidin-2-ones via site-selective difunctionalization of piperidine derivatives

An efficient and novel synthesis of 3-hydroxypiperidin-2-ones via site-selective difunctionalization of the inert C(sp³)?H bonds of N-substituted piperidine derivatives is presented. Mechanistically, the formation of the title compounds is believed to go through a cascade process featuring with the sequential formation of cyclic enamine, oxiranium and iminium as key intermediates.     

A convenient synthesis of copper(II) bis[5-(pyridin-2-yl-methylidene)-2-thiohydantoin] complexes

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Transition-metal-free sp3 C–H activation of 2-methylquinoline with terminal alkynes for synthesis of 3-(quinolin-2-yl)isoxazoles

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A green,isocyanide-based three-component reaction approach for the synthesis of multisubstituted ureas and thioureas

A one-pot, isocyanide based multicomponent protocol was presented starting from secondary amines towards (thio)urea derivatives and utilized for the construction of a diverse 27-membered chemical library. Following a green compatible microwave assisted condition, the formed N,N′-multisubstituted (thio)ureas were obtained in up to 85% yield.     

Metal-free selective synthesis of 2-substituted benzimidazoles catalyzed by Brönsted acidic ionic liquid: Convenient access to one-pot synthesis of N-alkylated 1,2-disubstituted benzimidazoles

A novel efficient method for the selective synthesis of 2-substituted benzimidazoles is described through condensation reaction of o-phenylenediamines with a wide rang of aliphatic, aromatic and heteroaromatic aldehyde substrates using Brönsted acidic ionic liquid as a reusable catalyst under metal-free conditions at ambient temperature. Notably, Dodecylimidazolium hydrogen sulfate ([DodecIm][HSO₄]) is the most efficient catalyst for good to excellent yields of the corresponding products (up to 98%). Subsequently, this protocol was successfully applied for the preparation of N-alkylated 1,2-disubstituted benzimidazoles in high to excellent yields via sequential one-pot reaction. In addition, catalysts are recycled at least four times without significant loss in activity.     

Convenient synthesis of N-(4-(2-aminopyridin-4-yl)thiazol-2-yl)-2-phenylacetamides

We report a facile one-pot, three-step synthesis of N-(4-(2-aminopyridin-4-yl)thiazol-2-yl)-2-phenylacetamides via condensation of 2-p-methoxybenzylamino-4-acetylpyridine with phenylacetylthioureas.     

Tandem and chemoselective synthesis of benzil derivatives from styrene and arene diazonium salts

A facile and practically applied protocol for synthesis of benzil derivatives using styrene and arene diazonium salts is reported. Pd(OAc)₂/SeO₂ catalytic system was found to be efficient for chemoselective synthesis of benzil. Selenium dioxide works well as an oxidant under milder reaction conditions. Moderate to very good yields of the desired products were obtained.     

Total synthesis of the proposed structure of xylarolide

A total synthesis of a proposed structure of xylarolide is described. The key features of the synthesis include Sharpless asymmetric reaction, Wittig olefination, Sharpless asymmetric dihydroxylation, Still-Gennari olefination and Yamaguchi lactonization. The differences in the spectroscopic data of the synthetic and natural product indicate a revision of the assigned structure.     

One-pot diastereoselective synthesis of tetrahydroepimino-benzo[b]azocines through sequential [3+2]-cycloaddition and Staudinger-aza-Wittig reactions

The one-pot synthesis of tetrahydro-epiminobenzo[b]azocines through a sequential 1,3-dipolar cycloaddition and intramolecular Staudinger-aza-Wittig reaction sequence is reported. This methodology provides a new and efficient approach for medium-sized and bridged nitrogen heterocyclic molecules.