Amido Form Research Articles

Aroylhydrazone‐based nickel(II) complexes: Synthesis and their structural, density functional theory (DFT), biological and catalytic studies

Nickel(II) complexes of tridentate NNO donor aroylhydrazones, viz., di‐2‐pyridyl ketone‐4‐methoxybenzhydrazone monohydrate (DKMBH·H2O) and 2‐acetylpyrazine‐4‐methoxybenzhydrazone monohydrate (APMBH·H2O), were synthesized and characterized using various methods, including spectral techniques (Fourier transform infrared [FT‐IR], UV–vis) and analytical methods (elemental and X‐ray diffraction [XRD] analysis). Single‐crystal XRD was used to elucidate the crystal structures of nickel(II) complexes 1 and 2. The XRD analysis revealed that the respective ligands coordinated to the Ni(II) center through the deprotonated iminolate form in complex 1 and the neutral amido form in complex 2, resulting in distorted octahedral geometries. The ground state electronic configurations of the complexes were studied using the B3LYP/UB3LYP levels of DFT. Using absorption spectral titration methods, the interactions of complexes with CT‐DNA and bovine serum albumin (BSA) protein were examined. The observed data demonstrate that the complexes adopt an intercalative binding mode to bind to CT‐DNA and BSA protein. Additionally, the antioxidant activity of the nickel(II) complexes and their ligands was determined using 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH). Complex 2 demonstrated the highest radical scavenging activity of the compounds studied (IC50 = 3.81 mM). Furthermore, molecular docking studies were performed to understand how the complexes can interact with the SARS‐CoV‐2 main protease. The results revealed that complex 2 had the highest docking score (−8.18 kcal/mol) when compared with the other complexes under study. Aside from their biological properties, the nickel complexes heterogenized on functionalized SBA‐15 showed promising catalytic activity, achieving 98% yield in the reduction of nitrobenzene, forming exclusively aniline as the end product.

Activated Mn-MACHO Complexes Form Stable CO2 Adducts.

Manganese(I) carbonyl complexes bearing a MACHO-type ligand (HN(CH2 CH2 PR2 )2 ) readily react in their amido form with CO2 to generate 4-membered {Mn-N-C-O} metallacycles. The stability of the adducts decreases with the steric demand of the R groups at phosphorous (R=isopropyl>adamantyl). The CO2 -adducts display generally a lower reactivity as compared to the parent amido complexes. These adducts can thus be interpretated as masked forms of the active amido catalysts and potentially play important roles as off-loop species or branching points in catalytic transformations of carbon dioxide.

Syntheses, structural characterizations, and catalytic activities of manganese(II)-aroylhydrazone complexes

An aroylhydrazone, di-2-pyridyl ketone-4-methoxybenzhydrazone monohydrate (DKMBH·H2O), and its three Mn(II) complexes, [Mn(DKMB)2]·H2O (1), [Mn(DKMB)Cl] (2), and [Mn(DKMB)NO3] (3), were synthesized. The physicochemical properties of the aroylhydrazone and metal complexes were revealed using various methods, e.g., Fourier transform infrared (IR) spectroscopy, ultraviolet-visible spectroscopy, mass spectrometry, and 1H nuclear magnetic resonance (NMR) spectroscopy, in addition to analyses such as CHN elemental and thermal analyses and molar conductivity studies. The molecular structures of the aroylhydrazone and manganese complex, 1 were elucidated using single-crystal X-ray diffraction (XRD) analyses.IR spectroscopy, 1H NMR spectroscopy, and single-crystal XRD showed that the aroylhydrazone occurred in the amido form in the solid state. According to the results of XRD, the aroylhydrazone coordinated to the Mn(II) center via the pyridine and azomethine N atoms and iminolate O atom, with a distorted octahedral geometry, in bis-ligated complex, 1.The results of IR spectroscopy further supported the tridentate character of the aroylhydrazone. Furthermore, the Mn complexes displayed potential as catalysts in cyclooctene epoxidation. Among the three Mn complexes, the use of [Mn(DKMB)2]·H2O (1) resulted in a 92% conversion, with an epoxide selectivity of 95%.

Supramolecular diorganotin(IV) complexes of N′-(2-hydroxynaphthalen-1-yl)methylene)formohydrazide: Synthesis, spectroscopic characterization, X-ray structure, antibacterial screening, cytotoxicity and docking study

Three organotin(IV) complexes [Me2SnL(1), Ph2SnL(2), tert-Bu2SnL(3)] have been synthesized by the reaction of a novel ligand N'-(2-hydroxynaphthalen-1-yl)methylene)formohydrazide (H2L) with dialkyltin(IV) dichlorides [R2SnCl2 (R = Me, Ph, tert-Bu) in presence of Et3N. The ligand and complexes have been characterized by elemental analysis, mass spectrometry, FT-IR, 1H, 13C and 119Sn NMR spectroscopic techniques. The spectroscopic data suggests coordination of ligand to the diorganotin(IV) moieties via oxygen nitrogen donor sites and five coordinated tin centers. The molecular structures of ligand (H2L) and complexes (1, 3) were also confirmed by single crystal X-ray analysis. The solid state structure of ligand showed it to be in the amido form whereas the single crystal X-ray analysis of complexes revealed the dibasic tridentate nature of ligand and monometallic nature of complexes. In both the complexes (1, 3) the Sn atom is in a distorted five-coordinate square pyramidal geometry with trigonality index(τ) 0.33 and 0.41, respectively. Packing diagrams reveal the important role of H…H, CH…π and O…H interactions in generating the supramolecular assembly. The antibacterial potential of all the compounds was investigated against two gram-positive bacteria (Bacillus subtilis, Stephlococcus aureus) and four gram-negative bacterial strains (Escherichia coli, Shigella flexenari, Pseudomonas aeruginosa, Salmonella typhi), using imipenem as the standard drug. Complex 2 exhibited highest activity against Bacillus subtilis and highest cytotoxicity against brine shrimp nauplii with LD50 1.01 μg/mL. Molecular Docking investigations revealed the best target protein, the positive impact of diphenyltin(IV) moiety on the compound-protein binding and the important role of hydrogen bonding, pi-pi and hydrophobic forces in such type of interaction.

Cobalt(II), copper(II) and zinc(II) complexes of di-2-pyridyl ketone-4- methoxybenzhydrazone: Preparation and characterization

A new aroylhydrazone ligand, di-2-pyridyl ketone-4-methoxybenzhydrazone (DKMBH∙H2O) and its three complexes with cobalt(II), copper(II) and zinc(II), labelled Co(DKMB)Cl (1), Cu(DKMB)Cl (2), and Zn(DKMB)Cl (3) have been prepared and structurally studied. The spectroscopic techniques like IR, UV-Vis, MS, and 1H NMR, as well as CHN analysis and thermal analysis, have been used to physico-chemically characterize the synthesized compounds. The IR and 1H NMR analyses have made clear that the aroylhydrazone remains in the amido form in the solid state. The IR spectral measurements further support the tridentate character of the NNO donor aroylhydrazone. In all complexes, pyridine nitrogen, azomethine nitrogen, and iminolate oxygen of the tridentate aroylhydrazone are involved to coordinate to the metal centre.

Crystallographic, spectroscopic and theoretical investigations on Ni(II) complexes of a tridentate NNS donor thiosemicarbazone

Five new nickel(II) complexes [Ni(L)NCS] (1b), [Ni(L)N3] (2), [Ni(L)N(CN)2] (3), [Ni(L)OAc] (4) and [Ni(HL)SO4] (5) of a thiosemicarbazone HL (where HL = 2-benzoylpyridine-N(4)-phenylthiosemicarbazone) including pseudohalides like thiocyanate, azide and dicyanamide have been synthesized and characterized by elemental analysis, magnetic susceptibility, FT-IR, electronic and NMR spectroscopic techniques. The interesting amido-iminol tautomerism enables the pro-ligand to exist in amido form as well as deprotonated iminol form thereby functioning as tridentate NNS donor, coordinating through pyridyl nitrogen atom, azomethine nitrogen atom and amido/iminolate sulfur atom in the complexes. The crystal structures were established by single crystal XRD analysis. Two different single crystals of the compound thiocyanato complex were obtained with and without DMF solvent molecule having triclinic and monoclinic lattices with P1- and P21/n space groups respectively. Also, the compound 2 is having a monoclinic lattice with P21/n space group. Nickel(II) exists in distorted square planar geometry in all the complexes. Further DFT calculations were carried out at B3LYP/TZVP level of theory to obtain an insight on the stability and the nature of frontier orbitals. Finally, electrostatic potential plots mapped on optimized geometries substantiate the noncovalent interactions found in their respective crystal structures.

Synthesis and characterization of a new aroylhydrazone ligand and its cobalt(III) complexes: X-ray crystallography and in vitro evaluation of antibacterial and antifungal activities

A new aroylhydrazone ligand, 2-benzoylpyridine-4-methoxybenzhydrazone (BPMBH) and its two cobalt(III) complexes, [Co(BPMB)2]NO3·1.5H2O (1) and [Co(BPMB)2]Cl·2H2O (2) have been synthesized and structurally characterized. The synthesized compounds are physico-chemically characterized by CHN analysis, molar conductivity, magnetic susceptibility measurements and spectroscopic techniques like MS, IR, UV and NMR. The high molar conductivity values of the complexes confirmed the presence of counter ions in the lattice of the cationic complexes. The molecular structure of the aroylhydrazone and its complexes have been resolved using single crystal XRD studies. In the solid state, the aroylhydrazone exists in the amido form as evident from the IR and XRD studies. The tridentate nature of the NNO donor aroylhydrazone was also confirmed from the IR spectral studies. XRD studies reveal that in all complexes, the tridentate aroylhydrazone coordinates to the Co(III) center via pyridine nitrogen, azomethine nitrogen and iminolate oxygen and found to possess distorted octahedral geometry. The complexes are bis-ligated cationic complexes in which chloride and nitrate ions act as counter ions. The antibacterial and antifungal activities of the aroylhydrazone and its Co(III) complexes have been screened against bacterial species Staphylococcus aureus, Enterobacter aerogenes, Bacillus subtilis, Streptococcus pyogenes, Klebsiella pneumonia, Salmonella typhi and Escherichia coli. The antifungal activity was also checked using fungi Aspergillus niger, Penicillium chrysogenum and Rhizopus oryzae. From the activity data we can infer that the metal complexes have better biological activity than the metal free ligand against the bacterial and fungal species which were tested.

Synthesis, spectroscopic characterization, X-ray structure, DFT calculations, and antimicrobial studies of diorganotin (IV) complexes of monotopic oxygen nitrogen donor Schiff base

Seven new diorganotin(IV) complexes, [Me2SnL] (1), [Et2SnL] (2), [(n-Bu2SnL] (3), [Ph2SnL] (4), [(n-Oct2SnL] (5), [tert-Bu2SnL] (6), and [n-BuClSnL] (7) have been synthesized from the reaction of N′-(2-hydroybenzylidene)-4-tert-butylbenzohydrazide (H2L) with the corresponding diorganotin(IV) dichloride/oxide or organotin(IV) chloride dihydroxide. The synthesized compounds were structurally characterized by FT-IR, multinuclear NMR (1H and 13C) spectroscopies, elemental analysis, mass spectrometry, DFT/(B3LYP) calculations, and, for ligand single crystal, X-ray diffraction analysis. Spectroscopic evidence affirms coordination of ligand to the dialkyltin(IV) moieties through oxygen nitrogen donor sites in iminol form. The 1 J(119Sn, 13C) coupling constants, 584-655 Hz and 2 J(119Sn-1H) coupling constant, 79 Hz for complex (1), suggest pentacoordination around Sn atom in solution. Single-crystal X-ray structure of ligand show its existence in amido form. Supramolecular architecture mediated by N(2)-H···O(2) and C-H…π interactions is formed in solid state. The DFT calculations have been performed to obtain various structure-based molecular properties as well as to support experimental results. The synthesized compounds were screened in vitro against various human pathogenic microbial strains. Escherichia coli and Staphylococcus aureus were most visibly inhibited by complexes (4) and (7). Highest antifungal activity was shown by compound (6) against Fusarium solani. Compound (3) displayed highest cytotoxicity among synthesized compounds with LD50 0.44μg/mL.

Facile synthesis, photophysical and electrochemical redox properties of octa- and tetracarboxamidophenylporphyrins and the first example of amido-imidol tautomerism in porphyrins

5,10,15,20-tetrakis(4′-carboxamidophenyl)porphyrin (1) and 5,10,15,20-tetrakis(3′,5′-dicarboxamidophenyl)porphyrin (2) have been synthesized in excellent yields and characterized by various spectroscopic techniques and cyclic voltammetric studies. Notably, 1 and 2 exhibited amido-imidol tautomerism in DMSO-d6. The imido tautomer (C(OH)NH) was stabilised in DMSO-d6 at 293 K while the same was converted into amido form (CONH2) at high temperature (418 K). This is a first example of amido-imidol tautomerism in porphyrins. The moderate electron withdrawing nature of imidol groups at meso-phenyl rings lead to 80–95 mV anodic shift in their first ring reduction potential whereas 50–110 mV anodic shift in first ring oxidation potential as compared to that of H2TPP.

The ligating versatility of pseudohalides like thiocyanate and cyanate in copper(II) complexes of 2-benzoylpyridine semicarbazone: Monomer, dimer and polymer

Three new copper(II) complexes [Cu(bpsc)(NCS)]n (1), [Cu(Hbpsc)(NCS)2] (2) and [Cu(bpsc)μ2(NCO)]2 (3) of a semicarbazone Hbpsc (where Hbpsc=2-benzoylpyridine semicarbazone) with pseudohalides like thiocyanate and cyanate have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measurements, FT-IR, UV–Vis and EPR spectral studies. The interesting amido-iminol tautomerism enables the proligand to exist in amido form as well as deprotonated iminolate form thereby functioning as tridentate NNO donor, coordinating through pyridyl nitrogen atom, azomethine nitrogen atom and amido/iminolate oxygen atom in the complexes. Versatile coordinating behavior of pseudohalides gives rise to complexes with different nuclearities. Single crystal XRD studies showed that [Cu(bpsc)(NCS)]n (1) is a one dimensional polymer connected by single end-to-end (μ1,3) thiocyanate bridges whereas [Cu(Hbpsc)(NCS)2] (2) is monomeric in nature in which copper(II) center is bonded to two terminal thiocyanate groups. [Cu(bpsc)μ2(NCO)]2 (3) is an end-on cyanato bridged binuclear species and found to exhibit packing polymorphism. In all complexes, g values in frozen DMF indicate the presence of the unpaired electron residing in the dx2-y2 orbital.

Crystal structure of (E)-N'-(5-bromo-2-hy-droxy-benzyl-idene)nicotinohydrazide monohydrate.

In the title compound, C13H10BrN3O2·H2O, the conformation about the azomethine double bond is E. The mol-ecule exists in the amido form with a C=O bond length of 1.229 (2) Å. There is an intra-molecular O-H⋯N hydrogen bond forming an S(6) ring motif. The whole mol-ecule is almost planar, with an r.m.s. deviation of 0.021 Å for all non-H atoms, and the dihedral angle between the planes of the pyridine and benzene rings is 0.74 (12)°. In the crystal, the water mol-ecule of crystallization links the organic mol-ecules via Ow-H⋯O, Ow-H⋯N and N-H⋯Ow hydrogen bonds and short C-H⋯Ow contacts, forming sheets lying parallel to (100). Within the sheets there is a weak π-π inter-action involving the pyridine and benzene rings [centroid-to-centroid distance = 3.8473 (15) Å]. The sheets are linked via C-H⋯Br inter-actions, forming a three-dimensional network.

N′-[(1E)-1-(2-Fluorophenyl)ethylidene]pyridine-3-carbohydrazide

The title compound, C14H12FN3O, adopts an E conformation with respect to the azomethine double bond whereas the N and methyl C atoms are in a Z conformation with respect to the same bond. The ketonic O and azomethine N atoms are cis to each other. The non-planar mol­ecule [the dihedral angle between the benzene rings is 7.44 (11)°] exists in an amido form with a C=O bond length of 1.221 (2) Å. In the crystal, a bifurcated N—H⋯(O,N) hydrogen bond is formed between the amide H atom and the keto O and imine N atoms of an adjacent mol­ecule, leading to the formation of chains propagating along the b-axis direction. Through a 180° rotation of the fluoro­phenyl ring, the F atom is disordered over two sites with an occupancy ratio of 0.632 (4):0.368 (4).

Snapshots of a Reversible Metal–Ligand Two‐Electron Transfer Step Involving Compounds Related by Multiple Types of Isomerism

AbstractAn unusual and very fast equilibrium between two isomers, [(cod)Rh–I{(bpa – 2H)0}IrI(cod)][rlhar2][(cod)RhI{(bpa – 2H)2–}IrI(cod)], which simultaneously display multiple types of isomerism: ligand–metal redox (electromerism), linkage, bond‐stretch and ring‐slippage isomerism, has been studied by NMR spectroscopy and DFT calculations. Both isomers have been isolated by making rational use of their thermodynamic parameters (ΔH° = +1.93 kcal mol–1; ΔS° = +7.8 cal mol–1 K–1), and have been characterized by X‐ray diffraction methods. The equilibrium that involves a two‐electron exchange between a redox noninnocent ligand, which transforms from a deprotonated amido form into an imine, and a metal that is reduced, could elucidate a thus far obscure step in the oxidative dehydrogenation of amines to imines.

Eco-friendly Flame Retardant (FR) Pet Fibers through P – N Synergism

Polyester forms a major constituent among the synthetic fiber industry. It is the most popular synthetic fiber because of its high strength and esthetic appeal. Polyester being highly crystalline, hydrophobic and devoid of reactive groups, it is difficult to introduce reactive phosphorus into the fiber structure through chemical reactions with the phosphorus compounds. Fairly large quantities of the FR chemicals have to be incorporated to achieve self-extinguishing behavior. Although not all Flame Retardant (FR) chemicals are hazardous, it is advisable from an ecological point of view to introduce minimum quantities of FR substances in the fiber structure. The present Paper tries to address the said problems in a small way, so that the PET fiber could be better acceptable. Therefore, graft co-polymerization of nitrogenous vinyl monomers has been carried out on the fiber followed by its reaction with phosphorus chemicals, thereby incorporating reactive phosphorus in the grafted substrate. It has been shown that a very small amount of the FR chemical could impart fire resistance of very high order to polyester. Self-extinguishing characteristic was achieved for poly (ethylene terephthalate) fibers with acrylamide-grafted-phosphorylated (AM-g-P) PET fibers containing just 0.189% phosphorus on-weight-of-fiber (owf). Similar results were obtained for methacrylamide-grafted-phosphorylated (MAm-g-P) polyester fibers at the 0.77% phosphorus content level. Efficiency of phosphorus in presence of nitrogen that was achieved was at 263% for acrylamide (AM) system, while it was −12% for acrylonitrile (AN-phosphorus combination). This is attributed to P-N synergism in case of the FR polyester system when the nitrogen is in the amido form present in AM and MAm monomers.

Amine-tethered N-heterocyclic carbene complexes of rhodium(I)

A new family of rhodium-diene based complexes has been developed that incorporates an N-heterocyclic carbene ligand with an N-donor tether. The ligand is denoted Mes[CNH] 2 (where Mes[CNH] is 2,4,6-Me3C6H2NC3H2NCH2CH2NH-2,4,6-Me3C6H2) and Mes[CN] for the amido form. The synthesis of the Mes[CNH] ligand involves reaction of N-mesitylimidazole with 2-chloroethyl-N-mesitylamine under melt conditions, followed by deprotonation with KN(SiMe3)2. The reaction of Mes[CNH] with [(diene)RhCl]2 results in the formation of the monodentate complexes, Mes[CNH]Rh(diene)Cl (where diene = 1,5-cyclooctadiene (COD): 3a; diene = 2,5-norbornadiene (NBD): 3b). Bidentate variants could be isolated as either a neutral species, Mes[CN]Rh(diene) 4a–4b, via deprotonation, or an ionic analogue such as [Mes[CNH]Rh(diene)]BF4 5a–5b by reaction with NaBF4. Compounds 4–5 are the first examples of rhodium compounds that contained a bidentate NHC ligand with a pendant amino or amido donor. Complexes 3–5 were characterized fully and the solid-state single crystal X-ray structures of 3a, 4a, and 5b are discussed. The utility of these complexes as catalyst precursors for hydrogenation reactions was examined and it was determined that these systems are not significantly more active than colloidal rhodium when parallel reactions were run. Various methods of transfer hydrogenations were also investigated with 3a, which did not yield an appreciable conversion of either benzophenone or N-benzylideneaniline as substrates.Key words: rhodium, N-heterocyclic carbene, catalysis, hydrogenation.

About the stability of Au(NH3) 4 3+ in aqueous solution

The transformations of Au(OH)4− in aqueous solutions (T = 20°C, I = 1) containing NH3 and NH4+ (pH 8.1–8.5) were studied. The most pronounced changes in the system occur in the range 0 > log [NH4+] > −2.0 (cAu = (1−10) × 10−4 mol/L, the monitoring time was about two weeks). When log [NH4+] > 0, Au(NH3)43+ dominates together with the amido form Au(NH3)3NH22+; when log [NH4+] < −2.0, no changes in the spectra are observed, probably, because of the very low rate of the processes. As cAu increases in the indicated range, the polymerization rate grows. The equilibrium constant for Au(NH3)3OH2+ + NH3 = Au(NH3)43+ + OH is log\( K_{4 OH, NH_3 } \) = −4.2 ± 0.3. This constant was used together with other constants, taking into account possible ligand effects, to estimate the formation constant of Au(NH3)43+: logβ4 = 47 ± 1, E3/0 = 0.64 ± 0.02 V, log\( \beta _{4 OH, NH_3 } \) = −8.5 ± 1 (substitution of 4 NH3 for 4 OH− in Au(OH)4−), log\( \beta _{4 CI, NH_3 } \) = 17.5 ± 1 (substitution of 4NH3 for 4Cl− in AuCl4−).

Structures of Silver Sulfonamides

The structures of silver sulfonamides were found to depend highly on the substituent at the amide nitrogen of the sulfonamide. Silver is coordinated to that nitrogen and the sulfonamide is in the amido form if no substituent is present or if the substituent is a phenyl, acetyl, or 2-pyrimidyl group. If the substituent is a 2-thiazolyl or 2-pyridinyl group, the sulfonamide is in the imido form and silver coordinates to the nitrogen of the substituent. Depending on the number of suitable donor atoms per sulfonamide, the silver compounds are charged or uncharged and the primary amino group may be involved in compzlexation.

Studies on absorption of drugs. VII. Absorption of isomeric N1-heterocyclic sulfonamides from the rat small intestines and relations between physicochemical property and absorption of unionized sulfonamides.

Absorption of isomeric N1-heterocyclic sulfonamides was studied from the rat small intestines employing isomeric N-methyl sulfonamides in addition to usual antibacterial sulfonamides. The physicochemical properties of the compounds were studied in reference to their isomeric form in solution. Following Shepherd's method sulfapyridine and sulfathiazole were confirmed to exist as imido form about 84% and 100% respectively in aqueous solution. N1-methyl derivatives and ring N-methyl derivatives were adopted as a model of amido form and imido form respectively and the differences of their physicochemical properties and absorption characteristics from undissociated molecules of their parent compounds were discussed. Also relations of physicochemical properties and absorption were persuaded following Hansch's method. And absorption rate constant of undissociated form of the compounds under study was likely to be related to partitioning to n-octanol and molecular weight.

Studies on metabolism of drugs. 8. On the glucuronide of sulfaphenazole in human.

The metabolism of sulfaphenazole (SP), i.e. N1-(1-phenylpyrazole-5-yl) sulfanilamide in the human body was investigated. The main metabolite was isolated and confirmed to be the N-glucuronide of SP. In order to determine the structure of this glucuronide, SP-N1-[methyl (tri-O-acetyl-β-D-glucopyranosid) uronate] (III) was synthesized from potassium salt of SP and methyl (2, 3, 4-tri-O-acetyl-1-bromo-1-deoxy-α-D-glucopyranosid) uronate. Hydrolysis of III with NH4OH gave both N1-glucuronide and ring N-glucuronide of SP in the ratio of about 2 to 1. Furthermore, N1-methyl and ring N-methyl derivatives of SP were prepared with CH2N2, and their infrared and ultraviolet spectra were compared with those of the conjugate to confirm the substituted position of the glucuronic acid. These evidences indicated that the extracted compound is an imido-type conjugate, carrying the glucuronic acid attached to the nitrogen in the pyrazole ring while SP itself takes the amido form. Therefore, the main metabolite of SP is a sodium 1-deoxy-[1-phenyl-5-(sulfanilimino)-3-pyrazolin-2-yl]-D-glucopyranosiduronate containing 1 mole of water of crystallization.

Alkylation by secondary alcohols. I. The reaction of xanthydrol with someN1-monosubstituted sulfanilamides and related compounds

Sulfanilamides were found to undergo alkylation with xanthydrol, yielding either mono- or di-xanthenyl derivatives. The site of substitution, common to all sulfanilamides having a free p-amino group, was shown to be the N4-position in the sulfanilamide molecule. Three additional unique reactive sites were observed. Sulfanilamides carrying a thiazole, thiadiazole, or pyridazine substituent in the N1-position were also alkylated on the annular nitrogen atom of the heterocyclic ring, the reaction having occurred from the imido tautomeric form. Sulfisoxazole (IK), on the other hand, reacted from the amido form to give the N1,N4-dixanthenyl derivative. Sulfadimethoxine (Ih) was substituted at carbon, as well as at nitrogen, to yield N4-xanthenyl-N1-(2,6-dimethoxy-5-(9-xanthenyl)-4-pyrimidyl)sulfanilamide.Sulfanilamides possessing pKavalues of about 5.5 were found to be sufficiently acidic to catalyze their own reaction with xanthydrol, and no external catalyst was necessary. The exceptional ease of formation of the xanthylium ion was postulated to be associated with the resulting stability of this carbonium ion by virtue of its acquired aromatic character.