A new,four component copper(Ⅰ)-catalyzed interrupted click/radical relay cascade has been developed.This unprecedented interrupted click reaction provides a rapid modular synthesis of triazole sulfones,important priv...A new,four component copper(Ⅰ)-catalyzed interrupted click/radical relay cascade has been developed.This unprecedented interrupted click reaction provides a rapid modular synthesis of triazole sulfones,important privileged heterocyclic pharmacophores which cannot be accessed by a traditional click reaction.Radical interception of cuprate-triazole,the key reaction intermediate formed in situ,is an important feature of this process.展开更多
The recent development of selective oxidation of aromatic sulfides with molecular oxygen was highlighted.The sulfoxides and sulfones could be obtained by simply switching the reaction media,i.e.,bis(2-butoxyethyl)ethe...The recent development of selective oxidation of aromatic sulfides with molecular oxygen was highlighted.The sulfoxides and sulfones could be obtained by simply switching the reaction media,i.e.,bis(2-butoxyethyl)ether(BBE)or poly(ethylene glycol)dimethyl ether(PEGDME).The application of the high-boiling-point polyether as an initiator and green media can eliminate the need of large quantities of additives and volatile solvents.This strategy represents an economic and eco-friendly method that could find potential applications.展开更多
A novel reaction of trimethylsilylated arylacetylenes with sulfonyl chlorides was performed in the presence of silver nitrate or triflate. Conjugated vinyl sulfones as dramatic products were obtained in moderate yield...A novel reaction of trimethylsilylated arylacetylenes with sulfonyl chlorides was performed in the presence of silver nitrate or triflate. Conjugated vinyl sulfones as dramatic products were obtained in moderate yields and with Z-selectivity. A free radical mechanism has been proposed to account for the formation of the products.展开更多
Abstract: We described the synthesis of two 5-substituted γ-lactams Ⅰand Ⅱ by sulfone-baaed α-amidoalkylation method. This constitiutes the formal synthesis of ant venom alkaloids 2 and 3 in racemic form. The key ...Abstract: We described the synthesis of two 5-substituted γ-lactams Ⅰand Ⅱ by sulfone-baaed α-amidoalkylation method. This constitiutes the formal synthesis of ant venom alkaloids 2 and 3 in racemic form. The key intermediate 18 for the chiral synthesis of 2 and 3 was prepared from new chiral sulfone 7 by the same method.展开更多
An electrochemical vicinal heterodifunctionalization of olefins for the synthesis ofβ-oxysulfones is described.With suitable choice of the conditions,including current,electrodes,and electrolyte,this oxidation reacti...An electrochemical vicinal heterodifunctionalization of olefins for the synthesis ofβ-oxysulfones is described.With suitable choice of the conditions,including current,electrodes,and electrolyte,this oxidation reaction proceeded efficiently in an undivided cell without the use of a stoichiometric chemical oxidant.In addition to the previously established synthesis ofβ-hydroxysulfones in the presence of water,minor modification of this protocol by using either external alcohol nucleophiles or internal carboxylic acid nucleophile also led to the synthesis ofβ-alkoxysulfones,andβ-sulfonyl lactones.展开更多
A convenient and regioselective sulfonylation/cyclization of 1,6-enynes with arylazo sulfones has been developed to access a series of sulfonylated γ-butyrolactams.The present reaction could be efficiently conducted ...A convenient and regioselective sulfonylation/cyclization of 1,6-enynes with arylazo sulfones has been developed to access a series of sulfonylated γ-butyrolactams.The present reaction could be efficiently conducted under catalyst-and additive-free conditions,in which C-S and C-C bonds were selectively constructed in one-pot procedure.展开更多
One novel carbon-carbon bond insertion reaction of arynes has been developed. By this reaction β-keto sulfones can insert the triple bond of arynes to prepare polysubstituted ortho-keto benzyl sulfones.
Polystyrene-supported selenomethyl-sulfonates have been prepared. These novel reagents were treated with LDA to produce selenium stabilized carbanions, which reacted with alkyl halide and epoxides, followed by selenox...Polystyrene-supported selenomethyl-sulfonates have been prepared. These novel reagents were treated with LDA to produce selenium stabilized carbanions, which reacted with alkyl halide and epoxides, followed by selenoxide syn-elimination, to give E-vinyl sulfones and -hydroxy-substituted-E-vinyl sulfones respectively.展开更多
Arenesulfonyl chloride undergoes a facile one-pot coupling reaction with active halides assisted by zinc to give the corresponding sulfones in acceptable yields.
In many reactions involving selenosulfonate or thiosulfonate,the sutfone group often leaves in form of benzenesutfinic acid or sodium benzenesulfinate.A one-pot two-step reaction of selenosulfonate with isocyanides an...In many reactions involving selenosulfonate or thiosulfonate,the sutfone group often leaves in form of benzenesutfinic acid or sodium benzenesulfinate.A one-pot two-step reaction of selenosulfonate with isocyanides and allyl alcohol under aqueous conditions to afford selenocarbamates and allyl sulfone compounds is reported.The sulfinic acid as the first-step side product is converted to the allyl sulfone compound by water promoted reaction with allyl alcohol.Water acts as both an oxygen source of selenocarbamates and as a promoter to drive the second step reactio n.The reactions have the advantages of mild conditions,green,environment-friendly,and high atomic economy.展开更多
As an attractive C1 synthon,carbon dioxide(CO_(2))has been extensively used in organic synthesis to produce carboxylic acids.In this research,stereoselective electrochemical carboxylation ofα,β-unsaturated sulfones ...As an attractive C1 synthon,carbon dioxide(CO_(2))has been extensively used in organic synthesis to produce carboxylic acids.In this research,stereoselective electrochemical carboxylation ofα,β-unsaturated sulfones has been developed under transition-metal-free conditions.All the cinnamic acids and the derivatives are obtained selectively in the E-configuration.Besides,arylpropiolates also can be produced from alkynyl sulfones.展开更多
The microwave-assisted coupling reaction of electrondeficient aryl halides with sulfinic acid salts through SNAr-based addition reactions within 5-30 min. No catalysts were required under our conditions.
（E）-α-Iodovinyl sulfones 1 underwent the Sonogashira coupling reactions with terminal alkynes 2 in piperidine at room temperature in the presence of 5 mol% of Pd（PPh3）4 and 10 mol% of CuI to stereospecifically af...（E）-α-Iodovinyl sulfones 1 underwent the Sonogashira coupling reactions with terminal alkynes 2 in piperidine at room temperature in the presence of 5 mol% of Pd（PPh3）4 and 10 mol% of CuI to stereospecifically afford the corresponding （Z）-2-sulfonyl-substituted 1,3-enynes 3 in high yields.展开更多
Polychlorinated dibenzothiophenes(PCDTs)and their corresponding sulfone(PCDTO2)compounds are a group of important persistent organic pollutants.In the present study,geometrical optimization and subsequent calculations...Polychlorinated dibenzothiophenes(PCDTs)and their corresponding sulfone(PCDTO2)compounds are a group of important persistent organic pollutants.In the present study,geometrical optimization and subsequent calculations of electrostatic potentials(ESPs)on molecular surface have been performed for all 135 PCDTs and 135 PCDTO2 congeners at the HF/6-31G*level of theory.A number of statistically-based parameters have been extracted.Linear relationship between gas-chromatographic retention index(RI)and the structural descriptors have been established by multiple linear regression.The result shows that two descriptors derived from positive electrostatic potential on molecular surface,■andπ,together with the molecular volume(Vmc)and the energy of the lowest unoccupied molecular orbital(ELUMO)can be well used to express the quantitative structure-retention relationship(QSRR)of PCDTs and PCDTO2.Predictive capability of the two models has been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient(RCV)of 0.996 and 0.997,respectively.Furthermore,the predictive power of the models is further examined for the external test set.Correlation coefficients(R)between the observed and predicted RI values for the external test set are 0.997 and0.998,respectively,validating the robustness and good prediction of our model.The QSRR model established may provide again a powerful method for predicting chromatographic properties of aromatic organosulfur compounds.展开更多
The generation of variousβ-chiral sulfones bearing chiral cyclic sulfinamides through photoredox-catalyzed sulfur dioxide insertion with asymmetric radical cyclization is described.This method features a broad substr...The generation of variousβ-chiral sulfones bearing chiral cyclic sulfinamides through photoredox-catalyzed sulfur dioxide insertion with asymmetric radical cyclization is described.This method features a broad substrate scope and excellent stereospecificity.Computational studies reveal that the dispersion interaction between sulfinyl group and CH_(2)SO_(2)Ph group plays a crucial role in the stereoselectivity control.展开更多
β-Chiral sulfones are structural motifs widely found in natural products and bioactive molecules, while also serving as important intermediates for the synthesis of valuable chiral scaffolds. In contrast to the rapid...β-Chiral sulfones are structural motifs widely found in natural products and bioactive molecules, while also serving as important intermediates for the synthesis of valuable chiral scaffolds. In contrast to the rapid growth of sulfur dioxide insertion chemistry over the last decade, enantioselective catalytic variants for accessing β-chiral sulfones, especially those bearing a quaternary carbon stereocenter, remain rare. Herein, we report an enantioselective copper/bisoxazoline catalyzed oxysulfonylation of alkenes to yield isoxazolinyl-containing β-chiral sulfones bearing quaternary carbon stereocenters with moderate to excellent yields and up to 96:4 er. The advantage and irreplaceability of this sulfur dioxide insertion catalytic system have been demonstrated by achieving transformations clearly unavailable with the previously reported sulfonyl chloride system. Additionally,the recoverability of the new-developed bisoxazoline ligand L9 and its reusability without any erosion of the catalytic activity and enantioselectivity further demonstrate the usefulness of the protocol.展开更多
An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite(K_(2)S_(2)O_(5))as a connector is developed for the synthesis of various lactam-substi...An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite(K_(2)S_(2)O_(5))as a connector is developed for the synthesis of various lactam-substituted alkyl sulfones.Notably,this process does not require a metal catalyst or metal powder reductant,highlighting its environmentally friendly features.The reaction demonstrates outstanding substrate adaptability and a high tolerance towards diverse functional groups.Furthermore,the biologically active molecules and commercially available drugs with a late-stage modification are also highly compatible with this transformation.Mechanistic studies revealed that the reaction proceeds through a single-step process involving intramolecular radical cyclization,"SO_(2)"insertion,and external alkyl incorporation.展开更多
Herein,we report a novel heterogeneous photocatalyst for radical-mediated oxidative oxysulfonylation of alkynes toβ-keto sulfones under environmentally benign conditions.The oxygen vacancy-rich semiconductor Nb2O5(la...Herein,we report a novel heterogeneous photocatalyst for radical-mediated oxidative oxysulfonylation of alkynes toβ-keto sulfones under environmentally benign conditions.The oxygen vacancy-rich semiconductor Nb2O5(labeled as OVs-N-Nb_(2)O_(5))could efficiently catalyze a wide range of alkynes,especially for those bearing electron-deficient substituents or internal alkynes,to their correspondingβ-keto sulfones in good to high yields with good tolerance of diverse functional groups under visible-light illumination.The late-stage modification of steroidal compounds and synthesis of bioactive molecules were also achieved via this procedure,highlighting its potential for practical applications.Meanwhile,the photocatalyst OVs-N-Nb_(2)O_(5) showed outstanding catalytic stability for successive recycles without appreciable loss in activity and selectivity.The critical role of oxygen vacancies on improving reaction activity and selectivity was clearly disclosed via control experiments and theoretical calculation.展开更多
A new protocol has been developed for the formation of C.Se and C.S bonds by the direct selenosulfonylation of alkenes.This protocol is operationally simplistic, has a wide substrate scope, uses readily available sele...A new protocol has been developed for the formation of C.Se and C.S bonds by the direct selenosulfonylation of alkenes.This protocol is operationally simplistic, has a wide substrate scope, uses readily available seleno and sulfonyl sources, and is amenable to gram-scale synthesis. This reaction represents a significant addition to the limited number of reactions available for the intermolecular selenide difunctionalization of alkenes and would be useful for the synthesis of sulfur-and selenium-containing molecules.展开更多
基金financial support from the Natural Science Foundation of China and Shandong Province(Nos.21971149,92156007,ZR2019ZD45,ZR2020KB005)the Fundamental Research Funds of Shandong University。
文摘A new,four component copper(Ⅰ)-catalyzed interrupted click/radical relay cascade has been developed.This unprecedented interrupted click reaction provides a rapid modular synthesis of triazole sulfones,important privileged heterocyclic pharmacophores which cannot be accessed by a traditional click reaction.Radical interception of cuprate-triazole,the key reaction intermediate formed in situ,is an important feature of this process.
文摘The recent development of selective oxidation of aromatic sulfides with molecular oxygen was highlighted.The sulfoxides and sulfones could be obtained by simply switching the reaction media,i.e.,bis(2-butoxyethyl)ether(BBE)or poly(ethylene glycol)dimethyl ether(PEGDME).The application of the high-boiling-point polyether as an initiator and green media can eliminate the need of large quantities of additives and volatile solvents.This strategy represents an economic and eco-friendly method that could find potential applications.
文摘A novel reaction of trimethylsilylated arylacetylenes with sulfonyl chlorides was performed in the presence of silver nitrate or triflate. Conjugated vinyl sulfones as dramatic products were obtained in moderate yields and with Z-selectivity. A free radical mechanism has been proposed to account for the formation of the products.
文摘Abstract: We described the synthesis of two 5-substituted γ-lactams Ⅰand Ⅱ by sulfone-baaed α-amidoalkylation method. This constitiutes the formal synthesis of ant venom alkaloids 2 and 3 in racemic form. The key intermediate 18 for the chiral synthesis of 2 and 3 was prepared from new chiral sulfone 7 by the same method.
基金Financial support was provided by Hong Kong RGC (No. 16302318)Shenzhen Science and Technology Innovation Committee (No. JCYJ20170818113708560)HKUST (No. IEG17SC03)
文摘An electrochemical vicinal heterodifunctionalization of olefins for the synthesis ofβ-oxysulfones is described.With suitable choice of the conditions,including current,electrodes,and electrolyte,this oxidation reaction proceeded efficiently in an undivided cell without the use of a stoichiometric chemical oxidant.In addition to the previously established synthesis ofβ-hydroxysulfones in the presence of water,minor modification of this protocol by using either external alcohol nucleophiles or internal carboxylic acid nucleophile also led to the synthesis ofβ-alkoxysulfones,andβ-sulfonyl lactones.
基金supported by the International Cooperation Project of Qinghai Province(No.2018-HZ-806)the Youth Innovation and Technology Project of Higher School in Shandong Province(No.2019KJC021)+3 种基金the Natural Science Foundation of Shandong Province(No.ZR2018MB009)the Qinghai Key Laboratory of Tibetan Medicine Research(No.2017ZJ-Y11)CAS“Light of West China”Program 2018Entrepreneurship Training Program for College Students(No.201910049)。
文摘A convenient and regioselective sulfonylation/cyclization of 1,6-enynes with arylazo sulfones has been developed to access a series of sulfonylated γ-butyrolactams.The present reaction could be efficiently conducted under catalyst-and additive-free conditions,in which C-S and C-C bonds were selectively constructed in one-pot procedure.
基金We are grateful to the National Natural Science Foundation of China （Nos. 20332060 and 2472072）
文摘One novel carbon-carbon bond insertion reaction of arynes has been developed. By this reaction β-keto sulfones can insert the triple bond of arynes to prepare polysubstituted ortho-keto benzyl sulfones.
文摘Polystyrene-supported selenomethyl-sulfonates have been prepared. These novel reagents were treated with LDA to produce selenium stabilized carbanions, which reacted with alkyl halide and epoxides, followed by selenoxide syn-elimination, to give E-vinyl sulfones and -hydroxy-substituted-E-vinyl sulfones respectively.
文摘Arenesulfonyl chloride undergoes a facile one-pot coupling reaction with active halides assisted by zinc to give the corresponding sulfones in acceptable yields.
基金the National Natural Science Foundation of China (Nos.21971174,21772137,21672157)the Ph.D.Programs Foundation of PAPD+2 种基金the Project of Scientific and Technologic Infrastructure of Suzhou (No.SZS201708)the Major Basic Research Project of the Natural Science Foundation of the Jiangsu Higher Education Institutions (No. 16KJA150002)Soochow University,and State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials for financial support。
文摘In many reactions involving selenosulfonate or thiosulfonate,the sutfone group often leaves in form of benzenesutfinic acid or sodium benzenesulfinate.A one-pot two-step reaction of selenosulfonate with isocyanides and allyl alcohol under aqueous conditions to afford selenocarbamates and allyl sulfone compounds is reported.The sulfinic acid as the first-step side product is converted to the allyl sulfone compound by water promoted reaction with allyl alcohol.Water acts as both an oxygen source of selenocarbamates and as a promoter to drive the second step reactio n.The reactions have the advantages of mild conditions,green,environment-friendly,and high atomic economy.
基金Financial support from the National Natural Science Foundation of China(No.21901041)the Fuzhou University(No.0041/511095)。
文摘As an attractive C1 synthon,carbon dioxide(CO_(2))has been extensively used in organic synthesis to produce carboxylic acids.In this research,stereoselective electrochemical carboxylation ofα,β-unsaturated sulfones has been developed under transition-metal-free conditions.All the cinnamic acids and the derivatives are obtained selectively in the E-configuration.Besides,arylpropiolates also can be produced from alkynyl sulfones.
基金the Municipal Government of Shanghai(No.03DZ19209)Shanghai Hua-Yi Group for financial support.
文摘The microwave-assisted coupling reaction of electrondeficient aryl halides with sulfinic acid salts through SNAr-based addition reactions within 5-30 min. No catalysts were required under our conditions.
基金the National Natural Science Foundation of China(No.20462002)Natural Science Foundation of Jiangxi Province(No.0420015)for financial support.
文摘（E）-α-Iodovinyl sulfones 1 underwent the Sonogashira coupling reactions with terminal alkynes 2 in piperidine at room temperature in the presence of 5 mol% of Pd（PPh3）4 and 10 mol% of CuI to stereospecifically afford the corresponding （Z）-2-sulfonyl-substituted 1,3-enynes 3 in high yields.
基金supported by the Science and Technology Project of Zhejiang Province(2016C33039)the Public Technology Research Project(Analysis and Measurement)of Zhejiang Province(LGC19B070004)+1 种基金State Key Laboratory of Environmental Chemistry and Ecotoxicology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences(KF2018-15)Natural Science Foundation of Zhejiang Province(LY18C030003)
文摘Polychlorinated dibenzothiophenes(PCDTs)and their corresponding sulfone(PCDTO2)compounds are a group of important persistent organic pollutants.In the present study,geometrical optimization and subsequent calculations of electrostatic potentials(ESPs)on molecular surface have been performed for all 135 PCDTs and 135 PCDTO2 congeners at the HF/6-31G*level of theory.A number of statistically-based parameters have been extracted.Linear relationship between gas-chromatographic retention index(RI)and the structural descriptors have been established by multiple linear regression.The result shows that two descriptors derived from positive electrostatic potential on molecular surface,■andπ,together with the molecular volume(Vmc)and the energy of the lowest unoccupied molecular orbital(ELUMO)can be well used to express the quantitative structure-retention relationship(QSRR)of PCDTs and PCDTO2.Predictive capability of the two models has been demonstrated by leave-one-out cross-validation with the cross-validated correlation coefficient(RCV)of 0.996 and 0.997,respectively.Furthermore,the predictive power of the models is further examined for the external test set.Correlation coefficients(R)between the observed and predicted RI values for the external test set are 0.997 and0.998,respectively,validating the robustness and good prediction of our model.The QSRR model established may provide again a powerful method for predicting chromatographic properties of aromatic organosulfur compounds.
基金supported by the National Natural Science Foundation of China(22171206)the Natural Science Foundation of Zhejiang Province(LZ23B020001)+1 种基金the Zhejiang Provincial Ten Thousand Talent Program(2023R5244)the Open Research Fund of School of Chemistry and Chemical Engineering,Henan Normal University(2020ZD04)。
文摘The generation of variousβ-chiral sulfones bearing chiral cyclic sulfinamides through photoredox-catalyzed sulfur dioxide insertion with asymmetric radical cyclization is described.This method features a broad substrate scope and excellent stereospecificity.Computational studies reveal that the dispersion interaction between sulfinyl group and CH_(2)SO_(2)Ph group plays a crucial role in the stereoselectivity control.
基金supported by the National Natural Science Foundation of China(22171206)the Natural Science Foundation of Zhejiang Province(Z23B020002,LY22B020003,)+1 种基金the Open Foundation of Hunan Provincial Key Laboratory of Controllable Preparation and Functional Application of Fine Polymers(E22307)the Open Research Fund of School of Chemistry and Chemical Engineering,Henan Normal University(2020ZD04)。
文摘β-Chiral sulfones are structural motifs widely found in natural products and bioactive molecules, while also serving as important intermediates for the synthesis of valuable chiral scaffolds. In contrast to the rapid growth of sulfur dioxide insertion chemistry over the last decade, enantioselective catalytic variants for accessing β-chiral sulfones, especially those bearing a quaternary carbon stereocenter, remain rare. Herein, we report an enantioselective copper/bisoxazoline catalyzed oxysulfonylation of alkenes to yield isoxazolinyl-containing β-chiral sulfones bearing quaternary carbon stereocenters with moderate to excellent yields and up to 96:4 er. The advantage and irreplaceability of this sulfur dioxide insertion catalytic system have been demonstrated by achieving transformations clearly unavailable with the previously reported sulfonyl chloride system. Additionally,the recoverability of the new-developed bisoxazoline ligand L9 and its reusability without any erosion of the catalytic activity and enantioselectivity further demonstrate the usefulness of the protocol.
基金the Scientific Research Fund of Hunan Provincial Education Department(21B0262 and 22B1094)the Natural Science Foundation of Hunan Province(2022JJ40857)the Hunan Provincial Innovation Foundation For Postgraduate(CX20230757)forfinancial support.
文摘An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite(K_(2)S_(2)O_(5))as a connector is developed for the synthesis of various lactam-substituted alkyl sulfones.Notably,this process does not require a metal catalyst or metal powder reductant,highlighting its environmentally friendly features.The reaction demonstrates outstanding substrate adaptability and a high tolerance towards diverse functional groups.Furthermore,the biologically active molecules and commercially available drugs with a late-stage modification are also highly compatible with this transformation.Mechanistic studies revealed that the reaction proceeds through a single-step process involving intramolecular radical cyclization,"SO_(2)"insertion,and external alkyl incorporation.
基金supportof the National Natural Science Foundation of China(Nos.22002178,22078350)the Natural Science Foundation of Shandong Province(ZR2020KB016)+1 种基金Shandong Energy Institute Fund(Grant No.SEll202138)Y.Y.alsothanks the Royal Society(UK)fora Newton Advanced Fellowship(NAF/R2/180695).
文摘Herein,we report a novel heterogeneous photocatalyst for radical-mediated oxidative oxysulfonylation of alkynes toβ-keto sulfones under environmentally benign conditions.The oxygen vacancy-rich semiconductor Nb2O5(labeled as OVs-N-Nb_(2)O_(5))could efficiently catalyze a wide range of alkynes,especially for those bearing electron-deficient substituents or internal alkynes,to their correspondingβ-keto sulfones in good to high yields with good tolerance of diverse functional groups under visible-light illumination.The late-stage modification of steroidal compounds and synthesis of bioactive molecules were also achieved via this procedure,highlighting its potential for practical applications.Meanwhile,the photocatalyst OVs-N-Nb_(2)O_(5) showed outstanding catalytic stability for successive recycles without appreciable loss in activity and selectivity.The critical role of oxygen vacancies on improving reaction activity and selectivity was clearly disclosed via control experiments and theoretical calculation.
基金supported by the National Natural Science Foundation of China (U1504210)the China Postdoctoral Science Foundation (2015M572110)Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis (130028651)
文摘A new protocol has been developed for the formation of C.Se and C.S bonds by the direct selenosulfonylation of alkenes.This protocol is operationally simplistic, has a wide substrate scope, uses readily available seleno and sulfonyl sources, and is amenable to gram-scale synthesis. This reaction represents a significant addition to the limited number of reactions available for the intermolecular selenide difunctionalization of alkenes and would be useful for the synthesis of sulfur-and selenium-containing molecules.
