Bromide 1a Research Articles

Cu(I)–N-heterocyclic carbene complexes bearing a naphthyl substituent: synthesis, characterization, and antimicrobial activities

A series of 1-(alkyl)-3-(1-naphthyl)imidazolinium bromides (2a–d) as N-heterocyclic carbene (NHC) precursors were synthesized from 3-(1-naphthyl)-1H-imidazolinium chloride (1). By reacting these NHC precursors with fresh CuCl, Cu(I)–NHC complexes (3a–d) were synthesized. The structures of the compounds were elucidated using 1H, 13C-NMR, FT-IR, ESI-MS, X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis, and elemental analysis techniques. The thermal properties of selected complexes were determined. Salts (1, 2a–d) and Cu(I)–NHC complexes (3a–d) were investigated against test microorganisms to determine their antimicrobial potency. The imidazolinium salts 2b and 2d displayed remarkable antibacterial efficacy, particularly against gram-positive bacteria; however, the corresponding Cu(I)–NHC derivatives (3a–d) did not exhibit a similar level of potency probably due to limited solubility. Overall, it can be concluded that incorporation of N-substituent species with O-heteroatoms, instead of benzyl, allyl, or hexyl groups on NHC, can enhance the activity against microbial derivatives.

Синтез и исследование строения 2-алкенилсульфанил-1-метилимидазолов

Derivatives of 1-methylimidazole-2-thiol (1) bearing substituents of various kinds are prom-ising ligands for modeling various enzymatic systems and structures with pharmacological activity. They are widely used as intermediates in the synthesis of organic compounds possessing biological activity (antitumor, antimicrobial, antidiabetic, antithyroid, antihistamine, antiprotozoal, and antiviral) as well as agrochemicals, dyes, photochemicals, corrosion inhibitors, epoxy hardeners, adhesives, and plastic modifiers. In the present paper we have studied the interaction between 1-methylimidazole-2-thiol 1 and prenyl bromide (2a), trans-cinnamyl chloride (2b), and butenyl bromide under various conditions for the first time. It has been found that selectivity of the alkylation reactions of compound 1 depends on the reaction conditions (alkylating agent, solvent, and base). Synthesis of individual 1-methyl-2-prenylsulfanylimidazole (3a) (yielding 78–86 %), 1-methyl-2-cinnamylsulfanylimidazole (3b) (yielding 94–97 %), and 2-(3-butenyl)sulfanyl-1-methyl-imidazole (4) (yielding 33–75 %) has been carried out by alkylation of 1-methylimidazole-2-thiol 1 with prenyl bromide 2a, trans-cinnamyl chloride 2b, and butenyl bromide, respectively, in the following systems: i-PrOH–i-PrONa, K2CO3–Me2CO (for 3а), MeOH–MeONa, i-PrOH–i PrONa, K2CO3–Me2CO, K2CO3–MeCN and i-PrOH–i-PrOК (for 3b), MeOH–MeONa, i PrOH–i-PrONa, K2CO3–Me2CO, K2CO3–MeCN, i-PrOH–i-PrOК and КОН–H2O–BTEAC (for 4). The structure of the synthesized compounds 3a,b and 4 has been studied and proved by mass spectrometry (GC–MS), as well as ¹H, ¹³C NMR spectroscopy. General predictable directions for fragmentation of the molecular ions of S-derivatives 3a,b and 4, which are accompanied by elimination of methyl/phenyl and thiol radicals, have been revealed. The evidence that alkylation reactions occur at the sulfur atom is the presence of signals for the –SCH2– protons in the region of 3.12–3.84 ppm in the 1Н NMR spectra of compounds 3a,b and 4. According to the 1Н NMR data, it has been found that alkylation of 1-methylmimidazole-2-thiol 1 at other conditions leads to formation of small quantities of by-products, such as N-alkenyl and S,N-dialkenyl derivatives, due to its thione-thiol tautomerism.

Synthesis of 1,3,4-Thiadiazole Derivatives Using Hydrazonoyl Bromide: Molecular Docking and Computational Studies

Alkyl phenylcarbamodithioates were reacted with hydrazonoyl bromide 1a, b in ethanol containing a catalytic amount of triethylamine solution to afford and 1,3,4-thiadiazole derevatives 5a, b, respectively. In the same manner, alkyl hydrazinecarbodithioate (6–10)a, b were reacted with the appropriate hydrazonoyl bromide (1a, b) in ethanol containing a catalytic amount of triethylamine solution to afford 1,3,4-thiadiazole derivatives (13–17), respectively. Moreover, hydrazonoyl bromide 1a or 1b was reacted with 5-phenyl-1,3,4-oxadiazole-2-thione 22A in refluxing chloroform containing triethylamine to give 1,3,4-thiadiazole derivatives 21a and b, respectively. Elemental analysis, spectral data, and an alternative synthetic route were used to confirm the structures of all the newly synthesized heterocyclic compounds. AutoDock was used to screen possible drugs. To screen potential medications, AutoDock was utilized. The antiviral medications chloroquine, hydroxychloroquine, and Lopinavir, as well as their synthesized components, were all tested. Confirmation comes from molecular docking and computational investigations. The results of a detailed exploration of the structural characterization of 5b and 13b using quantum chemistry methods calculated using the DFT (B3LYP) method with a 6-31 + g (d, p) basis set are presented in the computational study. The goal of this study was to investigate the molecular dynamics and structural characteristics that regulate chemical behavior, as well as to compare theoretical predictions with experimental results.

One-pot synthesis of sodium 3,4,5-triphenyl-1,2-diphospholide through direct functionalization of white phosphorus

Direct conversion of elemental white phosphorus (P4) to organophosphorus compounds is an attractive and challenging goal in sustainable phosphorus chemistry. We report here the one-pot reaction of P4, sodium metal and (1,2,3-triphenylcyclopropenyl)phosphonium bromides 1a,b to give exclusively sodium 3,4,5-triphenyl-1,2-diphospholide 2. An electrochemical method for following the conversion of 1,2,3-triphenylcyclopropenylphosphonium bromides to sodium 3,4,5-triphenyl-1,2-diphospholide is also presented.

Short and Atom-Economic Enantioselective Synthesis of the σ1-Receptor Ligands (S)- and (R)-Fluspidine-Important Tools for Positron Emission Tomography Studies.

Aryl bromides 2a and 2b bearing an alkynyl substituent in the o-position reacted with n-butyllithium and 1-benzylpiperidin-4-one in a one-pot Domino reaction to form ester 3 and aldehyde 5, respectively. Enantiomeric alcohols (R)-8 and (S)-8 were obtained by conjugate NaBH4 reduction of α,β-unsaturated ester 3 in the presence of chiral cocomplexes (R,R)-10 and (S,S)-10. Starting from orthoester 2a, the precursors (R)-8 and (S)-8 for the synthesis of fluspidine enantiomers (R)-1/[18F](R)-1 and (S)-1/[18F](S)-1 were obtained in only two reaction steps without additional steps for N-protection in an atom-economic manner in 95.6% ee and 97.2% ee, respectively.

Process Intensification for the Synthesis of 6-Allyl-6-azabicyclo[3.1.0]hex-3-en-2-ol from 1-Allylpyridinium Salt Using a Continuous UV-Light Photoflow Approach

A new home-made UV photochemical reactor (95 cm of irradiation zone) consisting of a 12 parallel quartz tubes flow reactor, PQT6 (95 cm under irradiation and an internal diameter of 0.6 cm) was assembled to perform photochemical transformations in continuous-flow. PQT6 was evaluated for the photoreaction of 1-allylpyridinium bromide (1a) to 6-allyl-6-azabicyclo[3.1.0]hex-3-en-2-ol (2a), in a continuous process. This technology provides reduced reaction times, continuous production of 2a, and a productivity of 129 mg h−1, corresponding to 1.94 g of isolated 2a after 15 h of irradiation.

Novel (N‐heterocyclic carbene)Pd(pyridine)Br2 complexes for carbonylative Sonogashira coupling reactions: Catalytic efficiency and scope for arylalkynes, alkylalkynes and dialkynes

New N,N′‐substituted imidazolium salts and their corresponding dibromidopyridine–palladium(II) complexes were successfully synthesized and characterized. Reactions of palladium bromide with the newly synthesized N,N′‐substituted imidazolium bromides (2a and 2b) in pyridine afforded the corresponding new N‐heterocyclic carbene pyridine palladium(II) complexes (3a and 3b) in high yields. Their single‐crystal X‐ray structures show a distorted square planar geometry with the carbene and pyridine ligands in trans position. Both complexes show a high catalytic activity in carbonylative Sonogashira coupling reactions of aryl iodides and aryl diiodides with arylalkynes, alkylalkynes and dialkynes.

Dicationic imidazolium salts as fluorescent probes for selective detection of Fe3+ ion in pure aqueous media

A series of N, N’-disubstituted imidazolium salts: 3-(4-cyanobenzyl)-1-((1-(4-cyanobenzyl)pyridin-1-ium-3-yl)methyl)-2-methyl-1H-imidazolium bromide (1a), 3-(naphthalene-2-ylmethyl)-1-((-1-(naphthalene-2-ylmethyl)pyridin-1-ium-3-yl)methyl)-2-methyl-1H-imidazolium bromide (1b), 3-(4-cyanobenzyl)-1-((1-(4-cyanobenzyl)pyridin-1-ium-3-yl)methyl)-2-methyl-1H-imidazolium hexafluorophosphate (1c) and 3-(naphthalene-2-ylmethyl)-1-((-1-(naphthalene-2-ylmethyl)pyridin-1-ium-3-yl)methyl)-2-methyl-1H-imidazolium hexafluorophosphate (1d) were synthesized in good to excellent yields. The physical and chemical properties of highly water soluble bromide salts (1a and 1b) were modulated by counter anion exchange with PF6 anion (1c and 1d). These probes detect Fe (III) ion over other metal ions such as Na+, K+, Ba2+, Mn2+, Mg2+, Fe3+, Fe2+, Ca2+, Cu2+, Cr3+, Co2+, Al3+, Pb2+ and Zn2+ in aqueous media by fluorescence “turn-off” mechanism. Fluorescence quenching was also observed in the case of Fe2+, Cr3+ and Cu2+ ions to some extent. The emission intensity of probe 1a was quenched by 92% on the subsequent addition of aliquots of Fe3+ ion in pure aqueous media. Job’s plot studies of 1a-Fe3+ complex confirmed the 1:1 stoichiometry. The Stern-Volmer (S-V) plot indicates the static type of quenching mechanism at even low concentrations. The detection limit for 1a was found to be 2.81 × 10−5 M.

EFFECT OF PHENACYLPYRIDINIUM SALTS ON BACTERIAL POPULATION IN LIGHT OLIVE-BROWN SOIL OF BUNDELKHAND REGION (U.P.) INDIA

Effect of phenacylpyridinium bromide (1a) and p-chlorophenacylpyridinium bromide (1b) was investigated on the soil bacterial population by plate dilution method. Based on the average total bacterial count at different concentrations of salts, it was observed that salt 1b was more bactericidal than salt 1a and deleterious effectivity increased with the increasing level. The greater antibacterial effect of salt 1b may probably be attributed to the presence of chlorine atom attached to benzene ring.

ChemInform Abstract: Tin Triflate Promoted Synthesis of Bicyclic and Tricyclic Sulfonyl Dihydropyrans.

Abstract Tin triflate-promoted one-pot intramolecular annulation of α-geranyl or α-farnesyl β-ketosulfones 3–4 affords the respective bicyclic or tricyclic sulfonyl dihydropyrans 5–6 in moderate to good yields via a cascade cation-olefin-carbonyl carbocyclization process. The starting materials 3 and 4 were obtained by K2CO3-mediated α-geranylation or α-farnesylation of β-ketosulfones 1 with bromides 2a or 2b. The structures of the key products were confirmed by X-ray crystallography.

A Modular Strategy for the Direct Catalytic Asymmetric α-Amination of Carbonyl Compounds

Summary Direct catalytic methods for the stereoselective introduction of various non-protected amines at the carbon atom adjacent to a carbonyl group remain elusive in synthetic chemistry, even though they offer the most straightforward entry to chiral α-aminocarbonyl compounds. Here, we demonstrate that the in situ activation of hydroxylamines with trichloroacetonitrile enables direct transfer of their amine moieties to the C-3 position of oxindoles with rigorous enantiocontrol under the catalysis of chiral 1,2,3-triazolium salts. This protocol provides a powerful and practical means of accessing optically active 3-aminooxindoles with a wide array of alkyl and aryl substituents on nitrogen. Other carbonyl compounds, such as β-ketoesters and α-cyanoesters, can also be directly transformed into the corresponding α-aminocarbonyls with high enantioselectivity.

Study of the antibacterial and antifungal activities of synthetic benzyl bromides, ketones, and corresponding chalcone derivatives.

Several applications of chalcones and their derivatives encouraged researchers to increase their synthesis as an alternative for the treatment of pathogenic bacterial and fungal infections. In the present study, chalcone derivatives were synthesized through cross aldol condensation reaction between 4-(N,N-dimethylamino)benzaldehyde and multiarm aromatic ketones. The multiarm aromatic ketones were synthesized through nucleophilic substitution reaction between 4-hydroxy acetophenone and benzyl bromides. The benzyl bromides, multiarm aromatic ketones, and corresponding chalcone derivatives were evaluated for their activities against eleven clinical pathogenic Gram-positive, Gram-negative bacteria, and three pathogenic fungi by the disk diffusion method. The minimum inhibitory concentration was determined by the microbroth dilution technique. The results of the present study demonstrated that benzyl bromide derivatives have strong antibacterial and antifungal properties as compared to synthetic chalcone derivatives and ketones. Benzyl bromides (1a and 1c) showed high ester activity against Gram-positive bacteria and fungi but moderate activity against Gram-negative bacteria. Therefore, these compounds may be considered as good antibacterial and antifungal drug discovery. However, substituted ketones (2a–b) as well as chalcone derivatives (3a–c) showed no activity against all the tested strains except for ketone (2c), which showed moderate activity against Candida albicans.

Tin triflate promoted synthesis of bicyclic and tricyclic sulfonyl dihydropyrans

Tin triflate-promoted one-pot intramolecular annulation of α-geranyl or α-farnesyl β-ketosulfones 3–4 affords the respective bicyclic or tricyclic sulfonyl dihydropyrans 5–6 in moderate to good yields via a cascade cation-olefin-carbonyl carbocyclization process. The starting materials 3 and 4 were obtained by K2CO3-mediated α-geranylation or α-farnesylation of β-ketosulfones 1 with bromides 2a or 2b. The structures of the key products were confirmed by X-ray crystallography.

ChemInform Abstract: Microwave Energized Synthesis of 2‐Aroylindole Derivatives: Piperidine/DMF as an Effective Medium

Abstractby reaction of aminoketones with phenacyl bromides

Photochemical Generation of Benzyl Cations That Selectively Cross-Link Guanine and Cytosine in DNA.

UV irradiation of several aryl boronates efficiently produced bifunctional benzyl cations that selectively form guanine-cytosine cross-links in DNA. Photoinduced homolysis of the C-Br bond took place with the aryl boronate bromides 3a and 4a, generating free radicals that were oxidized to benzyl cations via electron transfer. However, photoirradiation of the quaternary ammonium salts 3b and 4b led to heterolysis of C-N bond, directly producing benzyl cations. The electron-donating group in the aromatic ring greatly enhanced cross-linking efficiency.

Synthesis, structural study and biological activity of new derivatives of chrysin containing a 2-mercaptopyridyl or 5-(trifluoromethyl)-2-mercaptopyridyl fragments

New derivatives of chrysin containing 2-mercaptopyridine (2a–2e) or 5-(trifluoromethyl)-2-mercaptopyridine (3a–3e) moieties were prepared from the reaction between bromides (1a–1e) and 2-mercaptopyridine or 5-(trifluoromethyl)-2-mercaptopyridine, respectively. Their structures were elucidated by NMR, IR and elemental analysis. The molecular structure of compounds 1a, 1c–1e, 2b–2e and 3a was determined by single-crystal X-ray diffraction studies. All rings in these structures are nearly coplanar and they showed an intramolecular hydrogen bond between the phenolic hydroxyl H atom and the carbonyl O atom that forms a six membered ring. The crystal packing also showed a wide variety of intermolecular contacts such as C–H⋯A, π–π, C–H⋯π and lone pair⋯π interactions which were supported by quantum theory of atoms in molecules (QTAIM), Hirshfeld surface, and fingerprint plot analyses. Biological activity of all compounds was tested in growth assays of the nematode Caenorhabiditis elegans. Compounds 2e, 3b and 3c inhibited larval development.

Microwave‐Assisted Synthesis of Arylated Pyrrolo[2,1‐a]Isoquinoline Derivatives via Sequential [3 + 2] Cycloadditions and Suzuki‐Miyaura Cross‐Couplings in Aqueous Medium

Treatment of 5‐bromo‐2‐(bromoacetyl)thiophene (1) with isoquinoline gave the isoquinolinium bromide 2. Reaction of 2 with acrylic acid derivatives, in the presence of MnO2, afforded the 3‐[(5‐bromothiophen‐2‐ylcarbonyl]pyrrolo[2,1‐a]‐isoquinolines 3a, 3b. Suzuki–Miyaura cross‐coupling reactions of the bromides 3a, 3b in aqueous solvent with several activated and deactivated aryl(hetaryl)boronic acids 4a, 4b, 4c, 4d, 4e, 4f using a Pd(II)‐complex under thermal heating as well as microwave‐irradiating conditions afforded the corresponding new arylated pyrrolo[2,1‐a]isoquinoline derivatives 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 in high to excellent isolated yields.

Microwave Energized Synthesis of 2‐Aroylindole Derivatives: Piperidine/DMF as an Effective Medium

A convenient and efficient protocol has been developed for the synthesis of 2‐aroylindoles (3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 3j) in good yields by the reaction of 2‐aminoketones (1a, 1b, 1c) with phenacyl bromides (2a, 2b, 2c, 2d). The reaction success varied with different bases and solvents in both conventional and microwave methods. But finally, it was established that piperidine in DMF was an effective medium to carry out the reaction under microwave irradiation conditions.

Reactivity of thiazolidine-2-thione towards CuI/CuII: Synthesis and structures of [3-(2-thiazolin-2-yl)thiazolidine-2-thione]copper(I) bromide and [bis(2,2′-bipyridine)nitratocopper(II)] nitrate

Thiazolidine-2-thione (L1, NC3H5S2) reacted with copper(I) bromide in CH3CN under aerobic conditions and transformed through C–S bond cleavage into 3-(2-thiazolin-2-yl)thiazolidine-2-thione (L2, C3H4S2N-C3H4SN). This thio-ligand L2 with CuI ion yielded a three coordinate complex, [3-(2-Thiazolin-2-yl)thiazolidine-2-thione]copper(I)bromide 1a which crystallized in the triclinic system with the space group P1 as reported earlier. Treatment of 1a with bis(diphenylphosphino)methane (dppm) in dichloromethane also formed [3-(2-thiazolin-2-yl)thiazolidine-2-thione]copper(I) bromide 1b but it crystallized into the triclinic system with a new space group, P-1: 296(2) K, a, 7.3890(19); b, 8.473(2); c, 9.491(2) Å; α, 70.273(5); β, 67.170(5); γ, 84.949(5)∘; R, 6.79%. Reactions of copper(II) nitrate with thiazolidine-2-thione followed by the addition of 2,2′-bipyridine or with 2,2′-bipyridine first followed by the addition of thiazolidine-2-thione, gave blue crystals in both the cases. The x-ray crystallography revealed stoichiometry of the complex formed as: [Cu(κ 2-N,N′-bipy)2(κ 1-ONO2)](NO3)2, which crystallized in monoclinic crystal system with space group, P21/n(14). Crystal data: 173(2) K, a, 11.318(1), b, 12.160(1), c, 14.967(1) Å; β = 98.01(1)∘, R, 3.99%; 296(2) K, a, 11.340(5), b, 12.249(5), c, 15.065(6) Å; β = 98.04(2)∘, R, 4.09%. Thiazolidine-2-thione with copper(I) bromide in CH3CN under aerobic conditions yielded red brown crystals which on treatment with bis(diphenylphosphino)methane in dichloromethane formed [3-(2-thiazolin-2-yl)thiazolidine-2-thione]copper(I) bromide which crystallized into triclinic system with space group, P-1.

Perimidin-2-ylidene rhodium(I) complexes; unexpected halogen exchange and catalytic activities in transfer hydrogenation reaction

Four new [(NHC)RhCl(COD)] (NHC = perimidin-2-ylidene; COD = 1,5-cyclooctadiene) rhodium complexes (4a–c and 5a) have been prepared by the reaction of [Rh(μ-OMe)(COD)]2 with perimidinium bromides (2a–c and 3a). The halogen exchange, abstracted from 1,2-dichloroethane was observed during the reaction and [(NHC)RhCl(COD)] complexes were obtained instead of [(NHC)RhBr(COD)]. All ligand precursors and complexes have been fully characterized by 1H, 13C NMR, IR spectroscopy, elemental analysis and mass spectroscopy. X-ray diffraction studies on single crystals of 4a and 5a confirm the square planar geometry. The υ(CO) values of [(NHC)RhCl(CO)2] complexes (6a–c and 7a) revealed that the NHC ligands are not good σ-donors. Transfer hydrogenation (TH) reaction of aliphatic and aromatic ketones has been comparatively studied by using complexes 4a–c and 5a as catalysts.