Assessment of DNA Binding to Human Rad51 Protein by using Quartz Crystal Microbalance and Atomic Force Microscopy: Effects of ADP and BRC4‐28 Peptide Inhibitor

The interaction of human Rad51 protein (HsRad51) with single‐stranded deoxyribonucleic acid (ssDNA) was investigated by using quartz crystal microbalance (QCM) monitoring and atomic force microscopy (AFM) visualization. Gold surfaces for QCM and AFM were modified by electrografting of the in situ generated aryldiazonium salt from the sulfanilic acid to obtain the organic layer Au–ArSO₃H. The Au–ArSO₃H layer was activated by using a solution of PCl₅ in CH₂Cl₂ to give a Au–ArSO₂Cl layer. The modified surface was then used to immobilize long ssDNA molecules. The results obtained showed that the presence of adenosine diphosphate promotes the protein autoassociation rather than nucleation around DNA. In addition, when the BRC4‐28 peptide inhibitor was used, both QCM and AFM confirmed the inhibitory effect of BRC4‐28 toward HsRad51 autoassociation. Altogether these results show the suitability of this modified surface to investigate the kinetics and structure of DNA–protein interactions and for the screening of inhibitors.     

Initiator-Activation Strategy-Enabled Organocatalyzed Reversible-Deactivation Radical Polymerization Driven by Light

Organocatalyzed reversible-deactivation radical polymerizations (RDRPs) are attractive for many applications. Here, we developed photoredox-mediated RDRP by activating (hetero)aryl sulfonyl chloride (ArSO₂Cl) initiators with pyridines and designing a novel bis(phenothiazine)arene catalyst. The in situ formed sulfonyl pyridinium intermediates effectively promote controlled chain-growth from ArSO₂Cl, enabling access to various well-defined polymers with high initiation efficiencies and controlled dispersities under mild conditions. This versatile method allows “ON/OFF” temporal control, chain-extension, facile synthesis of different polymer brushes via organocatalyzed grafting reactions from linear chains. Time-resolved fluorescence decay studies and calculations support the reaction mechanism. This work provides a transition-metal-free RDRP to tailor polymers with readily available aromatic initiators, and will promote the design of polymerization leveraged from photoredox catalysis.     

Morphology Tailoring of Sulfonic Acid Functionalized Organosilica Nanohybrids for the Synthesis of Biomass‐Derived Alkyl Levulinates

Morphology evolution of sulfonic acid functionalized organosilica nanohybrids (Si(Et)Si‐Pr/ArSO₃H) with a 1D tubular structure (inner diameter of ca. 5 nm), a 2D hexagonal mesostructure (pore diameter of ca. 5 nm), and a 3D hollow spherical structure (shell thickness of 2–3 nm and inner diameter of ca. 15 nm) was successfully realized through P123‐templated sol–gel cocondensation strategies and fine‐tuning of the acidity followed by aging or a hydrothermal treatment. The Si(Et)Si‐Pr/ArSO₃H nanohybrids were applied in synthesis of alkyl levulinates from the esterification of levulinic acid and ethanolysis of furfural alcohol. Hollow spherical Si(Et)Si‐Pr/ArSO₃H and hexagonal mesoporous analogues exhibited the highest and lowest catalytic activity, respectively, among three types of nanohybrids; additionally, the activity was influenced by the ?SO₃H loading. The activity differences are explained in terms of different Brønsted acid and textural properties, reactant/product diffusion, and mass transfer rate, as well as accessibility of ?SO₃H sites to the reactant molecules. The reusability of the nanohybrids was also evaluated.     

New procedure for nucleophilic sulfonation of aromatic nitro compounds: Destructive oxidation of S-arylthioglycolic acids esters

A new reaction was discovered: oxidative destruction of sulfides of ArSCH₂CO₂Me type to sulfonic acids ArSO₃H effected by 70% HNO₃. This reaction was used to introduce an SO₃H group instead of aromatic nitro group activated only by meta-substituents: At treating with HSCH₂CO₂Me + K₂CO₃ the NO₂ group was substituted to form ArSCH₂CO₂Me with subsequent transformation into ArSO₃H. p-Fluoronitrobenzene behaved similarly (with replacement of the fluorine).     

Silber(I)‐di(arensulfonyl)amide und ein Silber(I)‐(arensulfonyl)(alkansulfonyl)amid: Von Bändern zu lamellaren Schichten mit kurzen Zwischenschichtkontakten C–H…Hal–C oder C–Br…Br–C

Structures of Ionic Di(arenesulfonyl)amides. 2. Silver(I) Di(arenesulfonyl)amides and a Silver(I) (Arenesulfonyl)(alkanesulfonyl)amide: From Ribbons to Lamellar Layers Exhibiting Short C–H…Hal–C or C–Br…Br–C Interlayer Contacts Low‐temperature X‐ray crystal structures are reported for AgN(SO₂C₆H₄‐4‐X)₂ · H₂O, where X is Cl ( 4 ) or Br ( 5 ), and for AgN(SO₂Ph)(SO₂Me) ( 6 ). Compounds 4 and 5 and the previously described F analogue ( 3 ) are isotypic, though not strictly isostructural (monoclinic, space group P2₁/c, Z = 4, but egregiously large discrepancies of x and z coordinates for corresponding atoms). Throughout this triad, glide‐plane related formula units are linked along the z axis to form infinite ribbons [(ArSO₂)₂N–Ag(μ‐H₂O)]_∞, in which Ag extends its coordination number to five by accepting one Ag–O bond from each of the (ArSO₂)₂N^⊖ ligands in the adjacent units. By means of O–H…O(S) hydrogen bonds, the ribbons are associated into lamellar layers parallel to the xz plane. Owing to the folded conformation of the anions, the layers display an inner polar region of Ag atoms, H₂O molecules and N(SO₂)₂ groups, outer apolar regions of stacked pairs of aryl rings, and interlayer regions hosting the halogen atoms. Inspection of the latter areas provides sound evidence that the distinct juxtapositions of adjacent layers arise from specific interlamellar attractions and repulsions ( 3 : two C–H…F, all F…F beyond the van der Waals limit d_W; 4 : one C–H…Cl, close packing of Cl atoms at Cl…Cl ≈ d_W; 5 : one C–H…Br, one short Br…Br contact < d_W, all other Br…Br > d_W). Structure 6 (monoclinic, P2₁/n, Z = 4) consists of a lamellar coordination polymer, in which the cation accepts one Ag–N and three Ag–O bonds drawn from four different anions. On account of crystal symmetry, the extended ligand has its Ph and Me groups distributed on both sides of the sheet, the phenyl rings forming the apolar regions of the lamella, whereas the smaller methyl groups are integrated into the corrugated inorganic region by means of weak C–H…O hydrogen bonds.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-aryl(methyl,trifluoromethyl)sulfonyl-1,4-benzoquinone monoimines with sodium sulfinates

In reactions with sodium sulfinates of N-substituted 1,4-benzoquinone monoimines with the quinoid ring having free positions 2 and/or 6 the fraction of products of 1,4-addition of the sulfinate ion grows in the series ArSO₂ → MeSO₂ → CF₃SO₂. In the case of 2,6-dimethyl derivatives the 1,6-addition is preferable, and the amount of products of 6,1-addition decreases.     

Access to Polysulfides through Photocatalyzed Dithiosulfonylation

In this study, we outline a general method for photocatalyzed difunctionalization of alkenes, a diene, alkynes, 1,3-enynes, and [1.1.1]propellane using dithiosulfonate reagents (ArSO₂-SSR) with improved atom economy. Both “ArSO₂-” and “-SSR” on the dithiosulfonate are transferred under mild conditions with broad substrate scope, high stereoselectivity, and complete regioselectivity. Significantly, the resulting dithiosulfonylated styrene is a general and practical nucleophilic disulfuration reagent, reacting with a variety of electrophiles efficiently. Both reactions can be conducted on gram scale, rendering the approach highly valuable.     

Collision-induced dissociation of negative ions in the gas phase: [Aryl S]−, [aryl SO]− and [aryl SO2]−

Collision-induced dissociation of the ions [ArS]^?, [ArSO]^? and [ArSO₂]^? has uncovered a rich and varied ion chemistry. The major fragmentations of [ArS]^? are complex and occur without prior ring hydrogen scrambling: for example, [C₆H₅S]^?→[C₂HS]^? and [HS]^?; [p-CD₃C₆H₄S]^?→[C₆H₄S]^?˙, [CD₃C₄S]^? and [C₂HS]^?. In contrast, all decompositions of [C₆H₅CH₂S]^? are preceded by specific benzylic and phenyl hydrogen interchange reactions. [ArSO₂]^? and [ArSO₂]^? ions undergo rearrangement, e.g. [C₆H₅SO]^?→[C₆H₅O]^? and [C₆H₅S]^?; [C₆H₅SO₂]^?→[C₆H₅O] ^?. The ion [C₆H₅CH₂SO]^? eliminates water, this decomposition is preceded by benzylic and phenyl hydrogen exchange.     

Efficient synthesis of sulfonylguanidines via reaction of tetra-substituted urine with ArSO2NCO

An efficient synthesis of sulfonylguanidines via reaction of tetra-substituted urines with ArSO₂NCO has been developed with good yields, which provides a convenient way for synthesis of sulfonyl group protected guanidine from urine in one step.     

Reaction of N-arylsulfonyl-2(3)-arylsulfonylamino-substituted 1,4-benzoquinonimines with sodium arylsulfinates

N-Arylsulfonyl-3-arylsulfonylamino-substituted 1,4-benzoquinonimine reacts with sodium arylsulfinates regiospecifically along 1,4-addition scheme; N-tosyl-2-(tosylamino)-substituted 1,4-benzoquinonimine regioselectively affords products of 1,4- and 6,3-addition with the latter prevailing. Arylsulfinate anion enters predominantly in the para-position with respect to the ArSO₂NH group.     

Reaction of N-acetyl- and N-[1-(arylsulfonylimino)ethyl]-1,4-benzoquinone imines with sodium arenesulfinates

N-Acetyl- and N-[1-(arylsulfonylimino)ethyl]-1,4-benzoquinone imines having no substituent in the 2- and/or 6-position of the quinoid ring react with sodium arenesulfinates preferentially according to the 1,4-addition pattern. The presence of an ArSO₂N group favors radical ion reaction with formation of 1,6-addition products.     

Reactions of arylsulfinyl chlorides and <Emphasis Type="Italic">N</Emphasis>-(arylsulfonyl)arylsulfinimidoyl chlorides with <Emphasis Type="Italic">p</Emphasis>-aminophenols

In reactions of arylsulfinyl chlorides and N-(arylsulfonyl)arylsulfinimidoyl chlorides with p-aminophenols formed N-arylthio-1,4-benzoquinone imines, evidently through a stage of N-arylsulfinyl-4-aminophenols and N-(N-arylsulfonyl)arylsulfinylimidoyl-4-aminophenols that under the reaction conditions eliminate respectively H₂O and ArSO₂NH₂.     

One-pot synthesis of imidazo[1,2-α]pyridine thioethers using imidazo[1,2-α]pyridines,arylsulfonyl chlorides and hydrazine

Abstract

A one-pot reaction of making RS-substituted imidazo[1,2-α]pyridine derivatives by directly using aryl or alkylsulfonyl chloride and hydrazine was developed, selectively giving good yields of the expected products. Compared with previously reported methods of using ArSO₂NHNH₂ as a sulfur source, this method is much cheaper, more practical and convenient and enriches current methods to make thioether-containing compounds, providing a good example of green chemistry.     

CATALYTIC EFFECTS IN THE AMINOLYSIS REACTIONS OF ARYLSULPHONIC ACID DERIVATIVES IN NON-AQUEOUS MEDIA

Abstract

The catalytic effects of organic bases in reactions of arylamines with arylsulphonic acid derivatives, ArSO₂X (X = Cl, Br, OSO₂Ar) in aprotic media are characterised by the following regularities. 1. The activity of 3- and 4-substituted pyridines, N-alkyl- and N-phenylimidazoles is desribed by the common Bränsted relationship. Substituents in positions 2 and 2,6 of the pyridine molecule have a strong steric influence. Tertiary cyclic amines of quinuclidine type with the same basicity as pyridines and imidazoles have more higher activity than the latter. N-Oxides of pyridine which are 4–5 pK_a units less basic than the corresponding pyridines have the catalytic activity 100 times as much, as compared with them. 2. The intensity of the catalytic action of pyridines and their N-oxides alters insignificantly with changing the leaving group X in the substrate, somewhat increasing in the order Cl < Br≤OSO₂Ar. 3. The activity of pyridine bases increases with increasing the solvent solvating ability. The inhibiting influence of the X^? anione on the rate of catalytic reaction displays in media of high polarity (nitrobenzene, acetonitrile). These regularities are explained in terms of the nucleophilic mechanism of catalysis which is supported by isolating intermediate adducts of tertiary amines (in particular 4-N,N-dimethylaminopyridine) with arylsulphonic acid bromides and anhydrides and by studies of their reactivity towards arylamines in methylene chloride. Compounds of bifunctional nature (carboxylic acids) do not accelerate the reaction under consideration unlike a similar substitution process at the carbonyl C-atom. The cause of this seems to be a different geometry of transition states in substitution at the sulpho group S-atom and at the carbonyl carbon, respectively.     

Ir‐Catalyzed C−H Amidation of Aldehydes with Stoichiometric/Catalytic Directing Group

Ir‐catalyzed sp² C?H amidation of aldehydes with various anilines as stoichiometric or catalytic directing groups was accomplished. A wide range of substrates were selectively amidated in good to excellent yields with broad functional group tolerance. The iridacycle complexes were isolated, characterized, and proved as key intermediates. Kinetic studies and Hammett plots provided detailed understandings of this amidation. According to the mechanism, the electron‐rich ArSO₂N₃ was proved effective for intermolecular sp³ C?H amidation.     

CYCLOADDITION-ELIMINATION REACTIONS OF 4-ALKYL-5-ARYLIMINO-1,2,3,4-THIATRIAZOLINES

Abstract

In previous work, we have shown that 4-alkyl-5-arylsulfonylimino-1,2,3,4-thiatriazolines (1, R = ArSO₂) react with unsaturated compounds (a=b) at the decomposition temperature of 1 via the intermediacy of a thiaziridinimine or its open-chain 1,3-dipole.     

Oxidation of γ-stannyl sulfides by monochloramine CB and hydrogen peroxide

The first γ-trimethylstannyl sulfimide, Me³Sn(CH₂)₃S(=NSO₂Ar)C₅H₁₁-n, was synthesized by oxidative imination of Me₃Sn(CH₂)₃SC₅H₁₁-n with ArSO₂(Na)Cl (Ar=C₆H₄Cl-4). Oxidation of γ-trimethylstannyl sulfimide by an alkaline solution of H₂O₂ gave γ-trimethylstannyl sulfoximide, Me₃Sn(CH₂)₃S(O)(=NSO₂Ar)C₅H₁₁-n, and γ-trimethylstannyl sulfone, Me₃Sn(CH₂)₃SO₂C₅H₁₁-n, the latter compound resulting from hydrolysis of the arylsulfimide group. Oxidation of stannyl sulfide by hydrogen peroxide yielded γ-trimethylstannyl sulfoxide, Me₃Sn(CH₂)₃S(O)C₅H₁₁-n (under mild conditions) or γ-trimethylstannyl sulfone (under more severe conditions). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 371–374, February, 1997.     

A comparative study on the dispersion behaviors and surface acid properties of molybdena on CeO2 and ZrO2 (Tet)

Dispersion of molybdena on CeO₂, ZrO₂ (Tet), and a mixture of CeO₂ and ZrO₂ (Tet), was investigated by using laser Raman spectroscopy (LRS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and temperature programmed reduction (TPR). The results indicate that molybdena is dispersed on both individual oxide support and mixed oxide support at the adopted molybdena loadings (0.2 and 0.8 mmol Mo⁶⁺/100 m²) and the structure of the supported molybdena species is intimate association with its loading amount. Two molybdena species are identified by Raman results, i.e. isolated MoO²⁻₄ species at 0.2 mmol Mo⁶⁺/100 m² and polymolybdate species at 0.8 mmol Mo⁶⁺/100 m². IR spectra of ammonia adsorption prove that isolated MoO²⁻₄ species are Lewis acid sites on the Mo/Ce and/or Zr samples, and the polymolybdate species are Brönsted acid sites on the Mo/Ce and/or Zr samples. Moreover, a combination of the Raman, IR and TPR results confirms that at 0.2 mmol Mo⁶⁺/100 m² Ce + Zr, molybdena is preferentially dispersed on the surface of CeO₂ when a mixed oxide support (CeO₂ and ZrO₂) is present, which was explained in term of the difference of the surface basicity between CeO₂ and ZrO₂ (Tet). Surface structures of the oxide supports were also taken into consideration.     

Assembling of 3,6-diazabicyclo[3.1.0]hexane framework in oxidative triflamidation of substituted buta-1,3-dienes

Reaction of trifluoromethanesulfonamide (triflamide) CF₃SO₂NH₂ with 2,3-dimethylbuta-1,3-diene (2) and 2,5-dimethylhexa-2,4-diene (3) in the oxidative system (t-BuOCl+NaI) results in the formation of 2,4-dimethyl- or 2,2,4,4-tetramethyl-3,6-bis(triflyl)diazabicyclo[3.1.0]hexane through two successive heterocyclizations. Reaction of diene (3) with arenesulfonamides ArSO₂NH₂ (Ar=Ph, Tol), stops at the formation of the product of oxidative 1,4-addition, N,N′-(2,3-dimethylbut-2-ene-1,4-diyl)diarenesulfonamides, providing evidence of the essential difference between the reactivity of triflamide and arenesulfonamides.     

An FTIR study of the Cl atom-initiated oxidation of CH2Cl2 and CH3Cl

The Cl atom-initiated oxidation of CH₂Cl₂ and CH₃Cl was studied using the FTIR method in the photolysis of mixtures typically containing Cl₂ and the chlorinated methanes at 1 torr each in 700 torr air. The results obtained from product analysis were in general agreement with those reported by Sanhueza and Heicklen. The relative rate constant for the Cl atom reactions of CH₂Cl₂ and CH₃Cl was determined to be k(Cl +CH₃Cl)/k(Cl + CH₂Cl₂) = 1.31 ± 0.14 (2σ) at 298 ± 2 K.