Asymmetric hydroamination of aminoallenes catalyzed by titanium and tantalum complexes of chiral sulfonamide alcohol ligands

A series of bidentate sulfonamide alcohol ligands with varying steric and electronic properties was synthesized. The titanium and tantalum complexes of these ligands, prepared in situ from either Ti(NMe₂)₄ or Ta(NMe₂)₅, were used as catalysts for the asymmetric hydroamination of 6-methyl-hepta-4,5-dienylamine, giving exclusively the α-vinylpyrrolidine product. The titanium derived catalysts gave products with low stereoselectivity, up to 11%ee favoring (+)-2-(2-methyl-propenyl)-pyrrolidine, while the tantalum derived catalysts gave products with higher and opposite stereoselectivity, up to 34%ee favoring (−)-2-(2-methyl-propenyl)-pyrrolidine.     

Molybdenum(V) chloride-catalyzed amidation of secondary benzyl alcohols with sulfonamides and carbamates

A general and selective method for the direct amidation of secondary benzyl alcohols with both sulfonamides and carbamates is described. This method has been applied to a variety of substrates and the reaction proceeded smoothly at room temperature in the presence of 5 mol % molybdenum(V) chloride to give the desired products in good yields.     

Stereoinversion of Unactivated Alcohols by Tethered Sulfonamides

The direct, catalytic substitution of unactivated alcohols remains an undeveloped area of organic synthesis. Moreover, catalytic activation of this difficult electrophile with predictable stereo‐outcomes presents an even more formidable challenge. Described herein is a simple iron‐based catalyst system which provides the mild, direct conversion of secondary and tertiary alcohols to sulfonamides. Starting from enantioenriched alcohols, the intramolecular variant proceeds with stereoinversion to produce enantioenriched 2‐ and 2,2‐subsituted pyrrolidines and indolines, without prior derivatization of the alcohol or solvolytic conditions.     

Palladium-catalyzed oxamidation of alkenes: A new approach to benzoxazolidines

A novel palladium catalyzed protocol for the synthesis of benzoxazolidine by the reaction sulfamidophenol and terminal alkene was developed. This oxamidation process is simple and does not require any ligand, base or inert atmosphere for the overall transformation. From control experiments, it is apparent that the cross-coupling reaction proceeds with initial formation of enesulfonamide which undergoes nucleopalladation by the intramolecular annulation and subsequent protodepalladation by TsOH to afford the benzoxazolidine.     

Eco-friendly and Cleaner Process Using Online Microwave-assisted Steam Extraction Coupled with Solid-phase Extraction for Trace Analysis of Sulfonamides in Animal Feed

An environmentally friendly method for extracting sulfonamides(SAs) residues from animal feed was described and applied. The method used online microwave-assisted steam extraction coupled with solid phase extraction(MASE-SPE), which was followed by the analysis using high performance liquid chromatography-mass spectrometry(HPLC-MS/MS). The SAs residues were extracted successively with water steam under microwave irradiation, and thus directly introduced into an SPE column containing cation-exchange resin. The SAs were then eluted with methanol-ammonia(90:10, volume ratio) from the SPE column and followed by HPLC-MS/MS. The limits of detection(LODs) for the analytes ranged from 0.24 ng/g to 0.49 ng/g. The limits of quantification(LOQs) ranged from 0.82 ng/g to 1.63 ng/g. Average recoveries of SAs were 76.3%-92.1%. The developed method was a reliable and environmentally friendly alternative to previous methods with respect to time, solvent and labor consumption for the analysis of SAs in animal foodstuffs.     

Stereoselective synthesis of hexahydroindoles and octahydrocyclohepta[b]pyrroles via gold(I)-catalyzed intramolecular 1,4-hydroamination of cyclic 1,3-dienes

The gold(I)-catalyzed intramolecular hydroamination of cyclohexa-1,3-dienes bearing an arylsulfonamide at the C-5 position proceeds in a 1,4-addition manner to afford hexahydroindole derivatives in a diastereoselective fashion and in good yields, whereas octahydrocyclohepta[b]pyrrole derivatives can be obtained from seven-membered ring substrates under the same reaction conditions. Coordination of the gold(I) species to the 1,3-diene at the double bond adjacent to the arylsulfonamide tether gave an η²-alkene gold complex. The anti-attack of the sulfonamide to the η²-alkene gold complex at the terminal position of the 1,3-diene resulted in the formation of the fused bicyclic ring with a newly formed Au-C bond at the allylic position. Allylic rearrangement of the η¹-allylgold complex followed by protodemetalation provided the fused heterobicyclic skeletons and regenerated the catalyst.     

Oxidative DNA cleavage by copper ternary complexes of 1,10-phenanthroline and ethylenediamine-sulfonamide derivatives

Ternary copper(II) complexes (1–3) of 1,10-phenanthroline and ethylenediamine-R-sulfonamide derivatives (R = benzene, toluene and naphthalene rings) have been synthesized and characterized with the aid of X-ray diffraction and spectroscopic and electrochemical techniques. The crystal structures of the complexes show that the coordination polyhedron around copper(II) is distorted square planar. Both 1,10-phenanthroline and ethylenediamine-R-sulfonamide act as bidentate ligands. The three structures are stabilized by π–π stacking interactions. The interaction of the complexes with calf thymus DNA has been investigated by thermal denaturation studies which indicated that DNA was stabilized in the presence of the compounds. The increase in DNA stability induced by the complexes follows the order: 3 > 2 > 1. All three complexes were found to be very efficient agents of plasmid DNA cleavage in the presence of ascorbate as reducing agent. Mechanistic studies of the DNA cleavage process performed with radical scavengers show that the reactive oxygen species involved in the DNA damage are the hydroxyl radical, singlet oxygen-like species, the superoxide* and hydrogen peroxide.     

Simple,rapid, and clean condensation of sulfonamide and maleic anhydride derivatives: Synthesis of novel 1H- Pyrrole-2,5-diones under heterogeneous conditions

H₆P₂W₁₈O₆₂ is used as an efficient catalyst for the synthesis of novel N-substituted sulfonyl maleimides (1H-Pyrrole-2,5-diones) via the condensation of sulfonamide and maleic anhydride derivatives. The Dawson heteropolyacid was used with a catalytic amount of 2 mmol% in acetonitrile at reflux. The reuse of H₆P₂W₁₈O₆₂ as heterogeneous catalyst several times without decrease in their activity, short reaction times, easy isolation of desired products with good to excellent yields shows the advantages of this novel methodology.     

Synthesis,spectral characterization,and antimicrobial studies of metal complexes of the Schiff base derived from [4-amino-N-guanylbenzene sulfonamide] and salicylaldehyde

Sulfaguanidinesalicylaldimine is a good bacteriostatic and a good complexing agent. Schiff-base complexes of Cu(II), Ni(II), Co(II), Zn(II), Cd(II), VO(IV), and UO₂(VI) have been synthesized. The structural features of the complexes have been confirmed by microanalytical data, FAB mass, IR, UV-Vis, ¹H-NMR, and EPR spectra. Molar conductance indicates the presence of nonelectrolytes. Spectroscopic and other analytical studies reveal the square-planar geometry for copper, square-pyramidal geometry for oxovanadium, seven-coordinate UO₂(VI) complex, and octahedral geometry for other complexes. The EPR spectrum of the copper complex in the powdered form at 77 K was recorded. The redox behavior of the copper and oxovanadium complexes was studied using cyclic voltammetry. Antimicrobial activities of the compounds have been studied against microorganisms such as Escherichia coli, Staphylococcus aureus, and Candida by well-diffusion technique in DMSO. Some of the complexes have higher activity than the free ligand and the standard.