A transition-metal-and oxidant-free amination/cyclization reaction to access 1,2,4-triazolo[1,5-a]pyridines was realized in water by using amino diphenylphosphinate as amino source.A broad array of readily accessible ...A transition-metal-and oxidant-free amination/cyclization reaction to access 1,2,4-triazolo[1,5-a]pyridines was realized in water by using amino diphenylphosphinate as amino source.A broad array of readily accessible N-(pyridyl)amides could be converted into the products featuring a diverse set of functional groups.The sustainable methodology was successfully applied to the late-stage functionalization of natural products and drugs.展开更多
A direct Michael addition reaction between imidazo[1,2-a]pyridines andα,β-unsaturated ketones using acidic alumina as a C(sp3)—H acid catalyst has been developed.The abundant C(sp3)—H acid sites(Al^(3+))on the aci...A direct Michael addition reaction between imidazo[1,2-a]pyridines andα,β-unsaturated ketones using acidic alumina as a C(sp3)—H acid catalyst has been developed.The abundant C(sp3)—H acid sites(Al^(3+))on the acidic alumina surface effectively activate the carbonyl group ofα,β-unsaturated ketones,significantly enhancing the electrophilicity of theβ-carbon and thereby facilitating selective alkylation at the C3 position of imidazo[1,2-a]pyridines.This method demonstrates excellent functional group compatibility,mild reaction conditions,low reagent costs,and operational simplicity,providing a novel strategy for the efficient synthesis of alkylated imidazo[1,2-a]pyridine derivatives.展开更多
We studied the cascade nucleophilic addition reactions of 1,2,3-triazines with activated acetonitriles or ketones,which were used to construct highly substituted pyridines that are not easily accessed by conventional ...We studied the cascade nucleophilic addition reactions of 1,2,3-triazines with activated acetonitriles or ketones,which were used to construct highly substituted pyridines that are not easily accessed by conventional methods.The strategy addressed some structural diversity issues currently facing medicinal chemistry,and the resulting pyridines could be used as convenient precursors for the synthesis of related pharmaceuticals.In particular,our method was applied to the syntheses of the marketed drug etoricoxib and several biologically important molecules in a few steps.展开更多
Herein,we report a Pd-catalyzed mono-a-arylation reaction for pyridine benzylic functionalization.This approach serves as an efficient alternative to synthesize di-heteroaryl acetates in good yields and selectivities....Herein,we report a Pd-catalyzed mono-a-arylation reaction for pyridine benzylic functionalization.This approach serves as an efficient alternative to synthesize di-heteroaryl acetates in good yields and selectivities.Moreover,the method is applicable to heteroa ryl substrate combinations,and exhibits great functional group tolerance.A streamlined protocol also enables the rapid synthesis of diheteroaryl ketones.The synthetic value was also demonstrated by scale-up experiments.展开更多
Condensation of β-Oxoanilide 1 with active methylene derivatives 2a,bafforded the pyridine derivative 5, and with crotononitrile afforded the pyridine 8. Compounds 9 and 11a-c were obtained by reaction of 1 with malo...Condensation of β-Oxoanilide 1 with active methylene derivatives 2a,bafforded the pyridine derivative 5, and with crotononitrile afforded the pyridine 8. Compounds 9 and 11a-c were obtained by reaction of 1 with malononitrile dimer and arylidinemalononitrile 10a-10c. In contrast, when compound 1 reacted with ethoxymethylen malononitrile afforded the pyridine derivative 13. On the other hand, treatment of 1 with anthranilic acid gave the quinoline derivative 14. Also, reactions of 1 with isothiocyanate derivatives afforded compounds 16-18. The reaction of 1 with chalcone derivative afforded the pyridine derivative 22. Treatment of compound 1 with thiourea produced pyrimidine derivative 23. Furthermore, compound 1 converted into pyrimidinethione 24a and pyrimidinone 24b on treatment with a mixture of aromatic aldehydes and thiourea or urea respectively. Reaction of 24a with hydrazonyl halide, thiosemicarbazide and arylidinecyanothioacetamide afforded compounds 26, 28 and 29. Compound 29 was treated with chloroacetonitrile to afford compound 30. Six compounds from the newly synthesized were screened for antibacterial and antifungal activity against bacteria staphylococcus aureus, bacillus cereus and klebsiella pneumonia and fungi aspergillus flavus and aspergillus ochraceous, respectively. Some of the tested compounds showed significant antimicrobial activity. IR, 1H NMR, mass spectral data, and elemental analysis elucidated the structures of all the newly synthesized compounds.展开更多
Palladium-catalyzed oxidative formal [4 + 1] annulation of pyridine-substituted acrylonitriles toward divergent fused N-heterocycles synthesis is reported. The heterodifunctionalization reaction with Cu(OAc);and urea ...Palladium-catalyzed oxidative formal [4 + 1] annulation of pyridine-substituted acrylonitriles toward divergent fused N-heterocycles synthesis is reported. The heterodifunctionalization reaction with Cu(OAc);and urea as the nitrogen source accesses to nitrile-substituted pyrazolo[1,5-a]pyridines in moderate to good yields, while the homodifunctionalization reaction with FeBr;leads to synthesis of nitrilesubstituted indolizines in excellent yields.展开更多
2-Amino-4-benzoyl-1-arylpyrrole-3-carbonitriles react with arylidene malonodinitriles, β-ketoesters and β- diketones to afford pyrrolo[2,3-b]pyridine derivatives.
A one-pot, three-component condensation reaction of an aldehyde, benzoyl acetonitrile （3-oxo-3-phenylpropane nitrile） and 6- amino-1,3-dimethylpyrimidine-2,4（1H,3H）-dione or 3-methyl-l-phenyl-lH-pyrazol-5-amine in...A one-pot, three-component condensation reaction of an aldehyde, benzoyl acetonitrile （3-oxo-3-phenylpropane nitrile） and 6- amino-1,3-dimethylpyrimidine-2,4（1H,3H）-dione or 3-methyl-l-phenyl-lH-pyrazol-5-amine in water to give fused pyrido[2,3- d]pyrimidines and pyrazolo[3,4-b]pyridines in high yields without any catalyst, is described.展开更多
A one-pot three component condensation synthesis of imidazo[1,5-a]pyridines using of various aromatic aldehydes and dipyridil ketone with ammonium acetate in the presence of Lithium chloride as catalyst in good yields...A one-pot three component condensation synthesis of imidazo[1,5-a]pyridines using of various aromatic aldehydes and dipyridil ketone with ammonium acetate in the presence of Lithium chloride as catalyst in good yields under microwave irradiation has been described.展开更多
The potentially bioactive 2-aryl-thiazolo[4,5-b]pyridines were synthesized via palladium-catalyzed desulfitative cross-coupling reaction between multisubstituted thiazolo[4,5-b]pyridine thioethers and boronic acids. Y...The potentially bioactive 2-aryl-thiazolo[4,5-b]pyridines were synthesized via palladium-catalyzed desulfitative cross-coupling reaction between multisubstituted thiazolo[4,5-b]pyridine thioethers and boronic acids. Yields of 48%–94% were obtained with copper（I） thiophene-2-carboxylate in the system.展开更多
Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free a,a＇-methylene positions such as cyclopentanone or cyclo...Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free a,a＇-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two a-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one a-methylene position alternatively resulted in 10-aryl-2,3：5,6-dibenzoacridines.展开更多
In this work, an efficient copper-catalyzed three-component reaction for the synthesis of sulfenylimidazo [1,2-a]pyridines using elemental sulfur as the sulfenylating agents has been developed. The reaction could proc...In this work, an efficient copper-catalyzed three-component reaction for the synthesis of sulfenylimidazo [1,2-a]pyridines using elemental sulfur as the sulfenylating agents has been developed. The reaction could proceed smoothly with a high degree of functional group tolerance and provide the desired products in moderate to good yield.展开更多
An efficient one-pot four-component reaction has been developed for the synthesis of 2,4-diarylcyclooctenopyridines, in moderate yields. This route is an effective modified two-step synthesis of Krohnke pyridine and i...An efficient one-pot four-component reaction has been developed for the synthesis of 2,4-diarylcyclooctenopyridines, in moderate yields. This route is an effective modified two-step synthesis of Krohnke pyridine and involves a four-component tandem reaction of pyridinium bromide with aromatic aldehydes and cyclooctanone in a system of NHaOAc/HOAc under microwave irradiation.展开更多
Interventions of metal complexes in the area of metallopharrneceutical and polymer sciences play a great economic importance to human challenges. Complexation behavior of some artemisinin derivatives with late transit...Interventions of metal complexes in the area of metallopharrneceutical and polymer sciences play a great economic importance to human challenges. Complexation behavior of some artemisinin derivatives with late transition metals and chromium-benzoimidazoylpyridine analogues have been investigated. The Fe（Ⅲ）, Zn（Ⅱ） and Cd（Ⅱ） complexes of artesunate and artemether and that of chromium-benzimidazoyl pyridine were synthesized with molar ratio of metal to ligand between 1：1 and 1：2. Structural elucidation using X-ray analysis and other characterization of the complexes （AAS, IR, UV, E.A, NMR） were carried out to explore the coordination affinity of them viz-a viz bonding, geometries and elemental composition. The IR absorption revealed that artesunate acts as monodentate specie through carbonyl group on coordination. However, its bidentate mode was also observed with carboxylic group acting as C=O and C-O bonding when deprotonation happened. Artemether （L2） was synthesized using artesunate and its structure was confirmed by single crystal X-ray crystallography as well as its Zn（Ⅱ） complex exhibiting a square planar geometry. A series of 2-benzoimidazoylpyridine derivates （L3-L6） and their chromium complexes were synthesized and characterized. In the presence of methylaluminoxane （MAO）, all chromium complexes show good activity for ethylene oligomerization and polymerization whereas with diethylaluminium chloride （Et2AlCl2） the complexes show moderate activity. The distribution of oligomers obtained follows Schulz- Flory rules with high selectivity for α-olefins. The combined productivity （meaning both activities of ethylene oligomerization and polymerization） are improved with increasing ethylene pressure. The results show that the reaction conditions greatly affect the properties of the polymer such as molecular weight distribution and melting point（Tm） with extremely broad molecular weight distributions. With elevating reaction temperature from 0 to 60 ℃, the melting point （Tin） of resultant polyethylene decreased rapidly from 134 ℃ to 70 ℃.展开更多
Under regular heating and microwave irradiation, 3-alkyl substituted imidazo[1,5-a] pyridines were synthesized from 2,2＇- pyridil, di-2-pyridyl ketone and aliphatic aldehydes in the presence of ammonium acetate and a...Under regular heating and microwave irradiation, 3-alkyl substituted imidazo[1,5-a] pyridines were synthesized from 2,2＇- pyridil, di-2-pyridyl ketone and aliphatic aldehydes in the presence of ammonium acetate and acetic acid. Compared to the traditional heating condition, the reaction time under microwave irradiation was shorter and 3-alkyl imidazo[1,5-a]pyddines were given in higher yield.展开更多
The exhaustive hydrodehalogenation(HDH)of CF_(3) groups in pyridines and of C(sp^(2))-X(X=F,Cl,Br,and I)bonds in pyridines and arenes was catalyzed by[Ni(COD)_(2)]employing NH3BH3 in the presence of KOtBu at room temp...The exhaustive hydrodehalogenation(HDH)of CF_(3) groups in pyridines and of C(sp^(2))-X(X=F,Cl,Br,and I)bonds in pyridines and arenes was catalyzed by[Ni(COD)_(2)]employing NH3BH3 in the presence of KOtBu at room temperature.The system showed a broad substrate scope,including OMe and NH2 substituted pyridines,and enabled the C(sp^(2))-X HDH of several environmental pollutants and the DDF of CF_(3) groups and C(sp^(2))-X bonds in pyridines,affording CD_(3)-substituted pyridines with d incorporation at the CD_(3) group in>99% and high degrees of d incorporation at the ring.Mechanistic studies for the HDF of 2-trifluoromethylpyridine allowed the identification of three simultaneous HDF cycles,with the first cycle being the rate-determining and the reaction of the[Ni(COD)_(2)]precatalyst with the H source being the entry pathway to the cycle.The key behind catalyst efficiency for exhaustive HDH and its broad substrate scope has been traced back to the use of KOtBu,which enabled hydride transfer from NH_(3)BH_(3) to the[Ni(COD)_(2)]precatalyst,rendering access to a nickelate(0)hydride complex responsible for C-F activation.Competition experiments employing pyridines allowed the rationalization of catalyst selectivity for different types of C(sp^(2))-X bonds and for C(sp^(2))-F vs.C(sp^(3))-F bonds,as well as the impact of the position of CF_(3) groups on catalyst efficiency.展开更多
The nickel(0)complex[Ni(^(iPr)PN)(COD)](^(iPr)PN=2-[(N-diisopropylphosphino)methylamino]pyridine,COD=1,5-cyclooctadiene)was an efficient precatalyst for the hydrodefluorination of pyridines employing pinacolborane(HBP...The nickel(0)complex[Ni(^(iPr)PN)(COD)](^(iPr)PN=2-[(N-diisopropylphosphino)methylamino]pyridine,COD=1,5-cyclooctadiene)was an efficient precatalyst for the hydrodefluorination of pyridines employing pinacolborane(HBPin).2-fluoro and 2,6-difluoropyridines were hydrodefluorinated at the 2-and 6-positions at room temperature in 3 h 30 min.The impact of the number of fluorine atoms and their position at the pyridyl ring in the efficiency of the catalyst was explored.Mechanistic experiments for the hydrodefluorination of 2,6-difluoropyridine allowed to identify COD decoordination followed by C–F oxidative addition as the catalyst entry pathway to the cycle and the[Ni(^(iPr)PN)(COD)]complex as the catalyst resting-state.The Ni(Ⅱ)fluoride complexes,[NiF(^(iPr)PN)(6-Fpy)](6-Fpy=6-fluoropyrid-2-yl)and[NiF(^(iPr)PN)(py)](py=2-pyridyl)were independently synthesized and identified as intermediates in the two subsequent hydrodefluorination cycles operative through single-turnover experiments.Both Ni(Ⅱ)fluoride complexes were found to be bench-stable precatalysts for the process with a comparable efficiency to[Ni(^(iPr)PN)(COD)]in the presence of a substoichiometric amount of COD to prevent catalyst deactivation.展开更多
The reactions of amides[tBu_(2)CarbAr_(2)]MN(SiMe_(3))_(2)(THF)(M=Ca(5),Yb(6))and[tBu_(2)CarbAr_(2)]MN(SiMe_(3))_(2)(M=Ca(7),Yb(8))coordinated by a bulky carbazolyl ligand(tBu_(2)CarbAr_(2)=3,6-di-tert-butyl-1,8-bis(3...The reactions of amides[tBu_(2)CarbAr_(2)]MN(SiMe_(3))_(2)(THF)(M=Ca(5),Yb(6))and[tBu_(2)CarbAr_(2)]MN(SiMe_(3))_(2)(M=Ca(7),Yb(8))coordinated by a bulky carbazolyl ligand(tBu_(2)CarbAr_(2)=3,6-di-tert-butyl-1,8-bis(3,5-di-tert-butylphenyl)-carbazolyl)with PhSiH_(3) allowed for the synthesis of isolable low-coordinate hydrides{[tBu_(2)CarbAr_(2)]MH(THF)}_(2)(M=Ca(11),Yb(12))and{[tBu_(2)CarbAr_(2)]MH(η^(6)-C7H8)}_(2)(M=Ca(11),Yb(12))featuring dimeric structures.Hydrides 11 and 12,as well as amides 7 and 8,proved to be efficient catalysts for PhSiH_(3) addition to pyridines at ambient T.However,the same catalyst at 90℃ catalyzes the opposite reaction:the release of the parent silane and the restoration of the aromatic pyridine system.展开更多
The C–H formylation of pyridines represents a valuable strategy for pyridine functionalization,as the resulting formylated pyridines can serve as versatile synthetic linchpins,enabling diverse transformations via the...The C–H formylation of pyridines represents a valuable strategy for pyridine functionalization,as the resulting formylated pyridines can serve as versatile synthetic linchpins,enabling diverse transformations via the formyl group.However,methods for regioselective meta-and para-formylation of pyridine have remained unexplored,and site-switchable strategies for introducing the same functional group are still scarce.Herein,we report a site-switchable metaand para-C–H formylation of pyridines proceeding via oxazino pyridine intermediates.The regioselectivity was precisely dictated by employing CHBr_(3)or CH_(3)OH as masked formyl equivalents under readily tunable conditions.This strategy enabled regioselective access to a structurally diverse array of formylated pyridines,while offering operational simplicity,broad functional group tolerance,scalability,and compatibility with late-stage modifications.Furthermore,the broad synthetic utility of formylated pyridines significantly enhanced the value of this method beyond mere formylation.Together with established ortho-formylation protocols,this work expands the synthetic toolbox for regioselective pyridine formylation,further broadening the accessible pyridine chemical space for applications in drug discovery and materials science.展开更多
Skeletal editing,especially for nitrogen-containing aromatic heterocycles,has become an increasingly important strategy for drug modification and development,enabling rapid compound diversification without the need fo...Skeletal editing,especially for nitrogen-containing aromatic heterocycles,has become an increasingly important strategy for drug modification and development,enabling rapid compound diversification without the need for de novo synthesis.Notably,despite their pervasiveness,established methods fall short in selective atomic swap due to the high stability of aromatic compounds.In this study,we report a CN-to-S atom swap approach for direct skeletal editing of pyridines into thiophenes via the addition of nucleophiles,ring-opening,and ring-closing(ANRORC)processes.Elemental sulfur,acting as an amphiphilic reagent,mediated this process through successive electrophilic and nucleophilic addition of the central sulfur atom at predictable sites.The power of this skeletal editing strategy was highlighted through the modification of the frameworks of natural products and drug molecules in a precise and controllable manner.展开更多
基金financial support from the National Natural Science Foundation of China(No.82003585)the Program for Science&Technology Innovation Talents in Universities of Henan Province(No.24HASTIT069)+5 种基金the Technical Innovation Team of Henan Normal University(No.2022TD03)the Special Project for Fundamental Research in University of Henan Province(No.23ZX009)the Henan Science and Technology Program(No.232102310364)the Key Project of Henan Educational Committee(No.22A150041)Excellent Youth Foundation of Henan Scientific Committee(No.222300420012)the Young Core Instructor Training Program of Xinyang Agriculture and Forestry University(2023)。
文摘A transition-metal-and oxidant-free amination/cyclization reaction to access 1,2,4-triazolo[1,5-a]pyridines was realized in water by using amino diphenylphosphinate as amino source.A broad array of readily accessible N-(pyridyl)amides could be converted into the products featuring a diverse set of functional groups.The sustainable methodology was successfully applied to the late-stage functionalization of natural products and drugs.
文摘A direct Michael addition reaction between imidazo[1,2-a]pyridines andα,β-unsaturated ketones using acidic alumina as a C(sp3)—H acid catalyst has been developed.The abundant C(sp3)—H acid sites(Al^(3+))on the acidic alumina surface effectively activate the carbonyl group ofα,β-unsaturated ketones,significantly enhancing the electrophilicity of theβ-carbon and thereby facilitating selective alkylation at the C3 position of imidazo[1,2-a]pyridines.This method demonstrates excellent functional group compatibility,mild reaction conditions,low reagent costs,and operational simplicity,providing a novel strategy for the efficient synthesis of alkylated imidazo[1,2-a]pyridine derivatives.
基金the financial support from the National Natural Science Foundation of China(No.21772019)Young Elite Scientist Sponsorship Program by CAST(No.2016QNRC001)+2 种基金The Fundamental Research Funds for the Central Universities(No.2019CDQYHG015)The Basic and Frontier Research Project of Chongqing(No.cstc2018jcyj AX0716)The Venture&Innovation Support Program for Chongqing Overseas Returnees(No.cx2019007)。
文摘We studied the cascade nucleophilic addition reactions of 1,2,3-triazines with activated acetonitriles or ketones,which were used to construct highly substituted pyridines that are not easily accessed by conventional methods.The strategy addressed some structural diversity issues currently facing medicinal chemistry,and the resulting pyridines could be used as convenient precursors for the synthesis of related pharmaceuticals.In particular,our method was applied to the syntheses of the marketed drug etoricoxib and several biologically important molecules in a few steps.
基金support by the National Natural Science Foundation of China (No.21702013)Beijing Natural Science Foundation (No.2184115)the Fundamental Research Funds from the Central Universities (Nos.XK1802-6,buctrc201721) in Beijing University of Chemical Technology
文摘Herein,we report a Pd-catalyzed mono-a-arylation reaction for pyridine benzylic functionalization.This approach serves as an efficient alternative to synthesize di-heteroaryl acetates in good yields and selectivities.Moreover,the method is applicable to heteroa ryl substrate combinations,and exhibits great functional group tolerance.A streamlined protocol also enables the rapid synthesis of diheteroaryl ketones.The synthetic value was also demonstrated by scale-up experiments.
文摘Condensation of β-Oxoanilide 1 with active methylene derivatives 2a,bafforded the pyridine derivative 5, and with crotononitrile afforded the pyridine 8. Compounds 9 and 11a-c were obtained by reaction of 1 with malononitrile dimer and arylidinemalononitrile 10a-10c. In contrast, when compound 1 reacted with ethoxymethylen malononitrile afforded the pyridine derivative 13. On the other hand, treatment of 1 with anthranilic acid gave the quinoline derivative 14. Also, reactions of 1 with isothiocyanate derivatives afforded compounds 16-18. The reaction of 1 with chalcone derivative afforded the pyridine derivative 22. Treatment of compound 1 with thiourea produced pyrimidine derivative 23. Furthermore, compound 1 converted into pyrimidinethione 24a and pyrimidinone 24b on treatment with a mixture of aromatic aldehydes and thiourea or urea respectively. Reaction of 24a with hydrazonyl halide, thiosemicarbazide and arylidinecyanothioacetamide afforded compounds 26, 28 and 29. Compound 29 was treated with chloroacetonitrile to afford compound 30. Six compounds from the newly synthesized were screened for antibacterial and antifungal activity against bacteria staphylococcus aureus, bacillus cereus and klebsiella pneumonia and fungi aspergillus flavus and aspergillus ochraceous, respectively. Some of the tested compounds showed significant antimicrobial activity. IR, 1H NMR, mass spectral data, and elemental analysis elucidated the structures of all the newly synthesized compounds.
基金financial support from the Natural Science Foundation of Jiangxi Provincial Education Department (Nos. GJJ201422, GJJ190754, GJJ190776)Science and Technology Project of Ganzhou City。
文摘Palladium-catalyzed oxidative formal [4 + 1] annulation of pyridine-substituted acrylonitriles toward divergent fused N-heterocycles synthesis is reported. The heterodifunctionalization reaction with Cu(OAc);and urea as the nitrogen source accesses to nitrile-substituted pyrazolo[1,5-a]pyridines in moderate to good yields, while the homodifunctionalization reaction with FeBr;leads to synthesis of nitrilesubstituted indolizines in excellent yields.
文摘2-Amino-4-benzoyl-1-arylpyrrole-3-carbonitriles react with arylidene malonodinitriles, β-ketoesters and β- diketones to afford pyrrolo[2,3-b]pyridine derivatives.
基金the financial support of the Research Council of the University of Isfahan
文摘A one-pot, three-component condensation reaction of an aldehyde, benzoyl acetonitrile （3-oxo-3-phenylpropane nitrile） and 6- amino-1,3-dimethylpyrimidine-2,4（1H,3H）-dione or 3-methyl-l-phenyl-lH-pyrazol-5-amine in water to give fused pyrido[2,3- d]pyrimidines and pyrazolo[3,4-b]pyridines in high yields without any catalyst, is described.
文摘A one-pot three component condensation synthesis of imidazo[1,5-a]pyridines using of various aromatic aldehydes and dipyridil ketone with ammonium acetate in the presence of Lithium chloride as catalyst in good yields under microwave irradiation has been described.
基金supported by the National Natural Science Foundation of China(No.21272009)
文摘The potentially bioactive 2-aryl-thiazolo[4,5-b]pyridines were synthesized via palladium-catalyzed desulfitative cross-coupling reaction between multisubstituted thiazolo[4,5-b]pyridine thioethers and boronic acids. Yields of 48%–94% were obtained with copper（I） thiophene-2-carboxylate in the system.
基金Supported by the National Natural Science Foundation of China(No.20672091)
文摘Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free a,a＇-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two a-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one a-methylene position alternatively resulted in 10-aryl-2,3：5,6-dibenzoacridines.
基金supported by the National Natural Science Foundation of China(Nos.21072054,21572051,21602057)the Ministry of Education of China(No.213027A)the Scientific Research Fund of Hunan Provincial Education Department(No.15A109)
文摘In this work, an efficient copper-catalyzed three-component reaction for the synthesis of sulfenylimidazo [1,2-a]pyridines using elemental sulfur as the sulfenylating agents has been developed. The reaction could proceed smoothly with a high degree of functional group tolerance and provide the desired products in moderate to good yield.
基金Supported by the National Natural Science Foundation of China(No.20672091)the Jiangsu Provincial Key Program of Physical Chemistry in Yangzhou University, China
文摘An efficient one-pot four-component reaction has been developed for the synthesis of 2,4-diarylcyclooctenopyridines, in moderate yields. This route is an effective modified two-step synthesis of Krohnke pyridine and involves a four-component tandem reaction of pyridinium bromide with aromatic aldehydes and cyclooctanone in a system of NHaOAc/HOAc under microwave irradiation.
文摘Interventions of metal complexes in the area of metallopharrneceutical and polymer sciences play a great economic importance to human challenges. Complexation behavior of some artemisinin derivatives with late transition metals and chromium-benzoimidazoylpyridine analogues have been investigated. The Fe（Ⅲ）, Zn（Ⅱ） and Cd（Ⅱ） complexes of artesunate and artemether and that of chromium-benzimidazoyl pyridine were synthesized with molar ratio of metal to ligand between 1：1 and 1：2. Structural elucidation using X-ray analysis and other characterization of the complexes （AAS, IR, UV, E.A, NMR） were carried out to explore the coordination affinity of them viz-a viz bonding, geometries and elemental composition. The IR absorption revealed that artesunate acts as monodentate specie through carbonyl group on coordination. However, its bidentate mode was also observed with carboxylic group acting as C=O and C-O bonding when deprotonation happened. Artemether （L2） was synthesized using artesunate and its structure was confirmed by single crystal X-ray crystallography as well as its Zn（Ⅱ） complex exhibiting a square planar geometry. A series of 2-benzoimidazoylpyridine derivates （L3-L6） and their chromium complexes were synthesized and characterized. In the presence of methylaluminoxane （MAO）, all chromium complexes show good activity for ethylene oligomerization and polymerization whereas with diethylaluminium chloride （Et2AlCl2） the complexes show moderate activity. The distribution of oligomers obtained follows Schulz- Flory rules with high selectivity for α-olefins. The combined productivity （meaning both activities of ethylene oligomerization and polymerization） are improved with increasing ethylene pressure. The results show that the reaction conditions greatly affect the properties of the polymer such as molecular weight distribution and melting point（Tm） with extremely broad molecular weight distributions. With elevating reaction temperature from 0 to 60 ℃, the melting point （Tin） of resultant polyethylene decreased rapidly from 134 ℃ to 70 ℃.
基金the Jiangsu Provincial Natural Science Foundation of China （No. BK2004092） the Scientific Research Foundation for the Returned 0verseas Chinese Scholars from State Education Ministry of China Nanjing University Talent Development Foundation.
文摘Under regular heating and microwave irradiation, 3-alkyl substituted imidazo[1,5-a] pyridines were synthesized from 2,2＇- pyridil, di-2-pyridyl ketone and aliphatic aldehydes in the presence of ammonium acetate and acetic acid. Compared to the traditional heating condition, the reaction time under microwave irradiation was shorter and 3-alkyl imidazo[1,5-a]pyddines were given in higher yield.
基金Victor Duran Arroyo and Roger Nunez for a generous gift of[Ni(^(iPr)PN)(COD)]the NSF for a LEAPS-MPS grant(#2316526)the University of California,Merced,for start-up funds.
文摘The exhaustive hydrodehalogenation(HDH)of CF_(3) groups in pyridines and of C(sp^(2))-X(X=F,Cl,Br,and I)bonds in pyridines and arenes was catalyzed by[Ni(COD)_(2)]employing NH3BH3 in the presence of KOtBu at room temperature.The system showed a broad substrate scope,including OMe and NH2 substituted pyridines,and enabled the C(sp^(2))-X HDH of several environmental pollutants and the DDF of CF_(3) groups and C(sp^(2))-X bonds in pyridines,affording CD_(3)-substituted pyridines with d incorporation at the CD_(3) group in>99% and high degrees of d incorporation at the ring.Mechanistic studies for the HDF of 2-trifluoromethylpyridine allowed the identification of three simultaneous HDF cycles,with the first cycle being the rate-determining and the reaction of the[Ni(COD)_(2)]precatalyst with the H source being the entry pathway to the cycle.The key behind catalyst efficiency for exhaustive HDH and its broad substrate scope has been traced back to the use of KOtBu,which enabled hydride transfer from NH_(3)BH_(3) to the[Ni(COD)_(2)]precatalyst,rendering access to a nickelate(0)hydride complex responsible for C-F activation.Competition experiments employing pyridines allowed the rationalization of catalyst selectivity for different types of C(sp^(2))-X bonds and for C(sp^(2))-F vs.C(sp^(3))-F bonds,as well as the impact of the position of CF_(3) groups on catalyst efficiency.
基金supported by funds from the NSF LEAPS-MPS-CHE program(grant#2316526 to R.A.)the NSF MRI program(CHE-2216471)University of California,Merced,start-up funds for Rebeca Arevalo.
文摘The nickel(0)complex[Ni(^(iPr)PN)(COD)](^(iPr)PN=2-[(N-diisopropylphosphino)methylamino]pyridine,COD=1,5-cyclooctadiene)was an efficient precatalyst for the hydrodefluorination of pyridines employing pinacolborane(HBPin).2-fluoro and 2,6-difluoropyridines were hydrodefluorinated at the 2-and 6-positions at room temperature in 3 h 30 min.The impact of the number of fluorine atoms and their position at the pyridyl ring in the efficiency of the catalyst was explored.Mechanistic experiments for the hydrodefluorination of 2,6-difluoropyridine allowed to identify COD decoordination followed by C–F oxidative addition as the catalyst entry pathway to the cycle and the[Ni(^(iPr)PN)(COD)]complex as the catalyst resting-state.The Ni(Ⅱ)fluoride complexes,[NiF(^(iPr)PN)(6-Fpy)](6-Fpy=6-fluoropyrid-2-yl)and[NiF(^(iPr)PN)(py)](py=2-pyridyl)were independently synthesized and identified as intermediates in the two subsequent hydrodefluorination cycles operative through single-turnover experiments.Both Ni(Ⅱ)fluoride complexes were found to be bench-stable precatalysts for the process with a comparable efficiency to[Ni(^(iPr)PN)(COD)]in the presence of a substoichiometric amount of COD to prevent catalyst deactivation.
基金The financial support of the Russian Science Foundation is highly acknowledged(Project No.23-73-10148)X-ray diffraction data were collected using the equipment of The Center for Molecular Composition Studies of INEOS RAS(Contract/agreement No.075-00277-24-00).
文摘The reactions of amides[tBu_(2)CarbAr_(2)]MN(SiMe_(3))_(2)(THF)(M=Ca(5),Yb(6))and[tBu_(2)CarbAr_(2)]MN(SiMe_(3))_(2)(M=Ca(7),Yb(8))coordinated by a bulky carbazolyl ligand(tBu_(2)CarbAr_(2)=3,6-di-tert-butyl-1,8-bis(3,5-di-tert-butylphenyl)-carbazolyl)with PhSiH_(3) allowed for the synthesis of isolable low-coordinate hydrides{[tBu_(2)CarbAr_(2)]MH(THF)}_(2)(M=Ca(11),Yb(12))and{[tBu_(2)CarbAr_(2)]MH(η^(6)-C7H8)}_(2)(M=Ca(11),Yb(12))featuring dimeric structures.Hydrides 11 and 12,as well as amides 7 and 8,proved to be efficient catalysts for PhSiH_(3) addition to pyridines at ambient T.However,the same catalyst at 90℃ catalyzes the opposite reaction:the release of the parent silane and the restoration of the aromatic pyridine system.
基金grant from Deutsche Forschungsgemeinschaft(DFG),Germany(grant no.STU 280/31-1)the Alexander von Humboldt Foundation,Germany(post-doctoral fellowship to S.-M.Guo).
文摘The C–H formylation of pyridines represents a valuable strategy for pyridine functionalization,as the resulting formylated pyridines can serve as versatile synthetic linchpins,enabling diverse transformations via the formyl group.However,methods for regioselective meta-and para-formylation of pyridine have remained unexplored,and site-switchable strategies for introducing the same functional group are still scarce.Herein,we report a site-switchable metaand para-C–H formylation of pyridines proceeding via oxazino pyridine intermediates.The regioselectivity was precisely dictated by employing CHBr_(3)or CH_(3)OH as masked formyl equivalents under readily tunable conditions.This strategy enabled regioselective access to a structurally diverse array of formylated pyridines,while offering operational simplicity,broad functional group tolerance,scalability,and compatibility with late-stage modifications.Furthermore,the broad synthetic utility of formylated pyridines significantly enhanced the value of this method beyond mere formylation.Together with established ortho-formylation protocols,this work expands the synthetic toolbox for regioselective pyridine formylation,further broadening the accessible pyridine chemical space for applications in drug discovery and materials science.
基金the Sichuan Science and Technology Program(grant nos.2024YFFK0016 and 2024ZYD0099)for the financial support.
文摘Skeletal editing,especially for nitrogen-containing aromatic heterocycles,has become an increasingly important strategy for drug modification and development,enabling rapid compound diversification without the need for de novo synthesis.Notably,despite their pervasiveness,established methods fall short in selective atomic swap due to the high stability of aromatic compounds.In this study,we report a CN-to-S atom swap approach for direct skeletal editing of pyridines into thiophenes via the addition of nucleophiles,ring-opening,and ring-closing(ANRORC)processes.Elemental sulfur,acting as an amphiphilic reagent,mediated this process through successive electrophilic and nucleophilic addition of the central sulfur atom at predictable sites.The power of this skeletal editing strategy was highlighted through the modification of the frameworks of natural products and drug molecules in a precise and controllable manner.
