Mohammad M. Ibrahim

Synthesis, Spectral Characterization and Fluorescent Assessment of 1,3,5-Triaryl-2-pyrazoline Derivatives: Experimental and Theoretical Studies

Two new pyrazoline derivatives, namely 5-(4-bromophenyl)-3-(5-chlorothiophen-2-yl)-1-phenyl-4,5-dihydro-1H-pyrazole (3) and 5-(4-bromophenyl)-3-(2,5-dichlorothiophen-3-yl)-1-phenyl-4,5-dihydro-1H-pyrazole (4) have been synthesized and characterized based on their spectral (IR, 1H and 13C NMR and MS) data and microanalysis. The fluorescence properties of 3 and 4 were studied by UV–Vis and emission spectroscopy. For compound 3, a fluorescence emission was observed in the blue region of the visible spectrum. The effect of different solvents on fluorescence was also investigated. Density Functional Theory calculations have also been performed to gain insight into geometric, electronic and spectroscopic properties of the pyrazoline derivatives. Both structures are analysed and compared in order to rationalize the different behaviour in 3 and 4.

One-Pot Synthesis , Characterization and Antimicrobial Activity of New 3-Cyano-4-Alkyl-6-(2,5-Dichlorothiophen-3-Yl)-2(1H)-Pyridones

The one-pot synthesis of new derivatives of 2(1H)-pyridone heterocycles carrying a thiophene nucleus is described. The reactions were carried out via the condensation of 3-acetyl2,5-dichlorothiophene and different alkyl aldehydes 2a-f with ethyl cyanoacetate in presence of ammonium acetate. The pyridone derivatives 3a-f were obtained in 63-86% yields and short reaction times. The antimicrobial activities of the new compounds were evaluated against some common Gram negative and Gram positive bacteria and fungi.

Synthesis of Fluorescent 1-(3-Amino-4-(4-(tert-butyl)phenyl)−6-(p-tolyl)furo[2,3-b]pyridin-2-yl)ethan-1-one: Crystal Structure, Fluorescence Behavior, Antimicrobial and Antioxidant Studies

Furopyridine III, namely 1-(3-amino-4-(4-(tert-butyl)phenyl)-6-(p-tolyl)furo[2,3-b]pyridin-2-yl)ethan-1-one, synthesized from 4-(4-(tert-butyl)phenyl)-2-oxo-6-(p-tolyl)-1,2-dihydropyridine-3-carbonitrile I in two steps. The title compound is characterized by NMR, MS and its X-ray structure. The molecular structure consists of planar furopyridine ring with both phenyl rings being inclined from the furopyridine scaffold to a significant different extent. There are three intramolecular hydrogen bonds within the structure. The lattice is stabilized by N—H…O, H2C—H …π and π…π intermolecular interactions leading to three-dimensional network. Compound III exhibits fluorescent properties, which are investigated. Antimicrobial potential and antioxidant activity screening studies for the title compound III and the heterocyclic derivatives, I and II, show no activity towards neither bacterial nor fungal strains, while they exhibited weak to moderate antioxidant activity compared to reference.

Synthesis, characterization and antimicrobial activity of new chalcones and their 6-aryl-4-(2,5-dichlorothiophen-3-yl)-6H-1,3-thiazin-2-amine derivatives

GRAPHICAL ABSTRACT ABSTRACT Chalcones (5a-h) were prepared in high yields via the condensation of 3-acetyl-2,5-dichlorothiophene (3) with aryl aldehydes (4a-h). The reaction of the resulting chalcones with thiourea in the presence of a catalytic amount of hydrochloric acid provided the 1,3-thiazin-2-amine derivatives (6a-g) in moderate yields. All new compounds were characterized by extensive NMR analysis data, including 1D NMR experiments (1H and 13C) and 2D NMR experiments (COSY, HMBC, HSQC), as well as ESIMS and HRESIMS data. The newly synthesized compounds were evaluated for their biological activities, which demonstrate a very good to low bioactivities as antibacterial and antifungal, respectively.

Crystal, Molecular Structure and DFT Study of 2,6,7-Trimethyl-3- p -tolylquinoxaline and 2-(4-Methoxyphenyl)-3,6,7-trimethylquinoxaline

The molecular structure of 2,6,7-trimethyl-3-p-tolylquinoxaline (hereafter denoted I) was confirmed by single crystal X-ray structure analysis. In the title compound, C18H18N2, I, the quinoxaline ring system is essentially planar. The phenyl ring at the 2-position makes a dihedral angle of 40.23° with the quinoxaline mean plane. In the crystal, molecules are linked into layers mainly by H2C–H···π and (π)C–H···π interactions. Stacking π···π interactions are absent in the structure. The experimental and theoretical structural aspects of I and the recently reported methoxy derivative, 2-(4-methoxyphenyl)-3,6,7-trimethylquinoxaline, II, have been investigated and compared. Experimental geometric parameters (bond lengths and bond angles and dihedral angles) were compared with computed values from density functional theory with B3LY6−31G(d,p) basis set. Results show that values are in good agreement. The highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) energies have been also calculated and used to determine the charge transfer within the molecule. MEP surfaces analyses were performed by the DFT method. From the MEP map, negative region is mainly localized over the electronegative nitrogen atoms (in I), and the nitrogen and oxygen atoms (in II) and the maximum positive region is localized on the methyl groups. These surfaces seem to correlate well with the intermolecular interactions in the lattice. Time-dependent density functional theory has been carried out to study the UV spectra of both molecules in gas phase and in methanol using polarizable continuum model and the results are presented and discussed.Graphical AbstractCrystal, molecular structure, crystal supramolecularity and DFT calculations of 2,6,7-Trimethyl-3-p-tolylquinoxaline and 2-(4-Methoxyphenyl)-3,6,7-trimethylquinoxaline are reported.

The Reaction of Cyanamidium Salts with Ylidenecyanamide Derivatives

Cyanamidium salts 1undergo ene reactions with ylidenecyanamide derivatives 5to afford conjugated iminium salts 12. The N,N,Nʹ-trialkylcyanamidium salts 1react as the ene, and the ylidenecyanamide derivatives 5react as the enophile components to form the 2-azoniaallene salts 11 followed by the formation of conjugated iminium salts 12 as cationic polynitrogen compounds with guanidine and amidine subgroups. The constitution of the new conjugated iminium salts 12 was secured by elemental analyses and spectroscopic data (IR and NMR). Graphical Abstract The Reaction of Cyanamidium Salts with Ylidenecyanamide Derivatives

3-Methyl­amino-3-phenyl­propan-1-ol

The title compound, C10H15NO, is an amino alcohol with the hydroxy group residing on the terminal C atom. Apart from the hydroxy group and the phenyl ring, all non-H atoms are almost coplanar. In the crystal, classical O—H⋯N and N—H⋯O hydrogen bonds connect the molecules into centrosymmetric dimers [R 2 2(12) descriptor] and tetrameric units [R 4 4(8) descriptor] as ring motifs, consolidating a three-dimensional network.

Concise Synthesis and Displacement Reactions of Model 3-(Alkylthio)- 6-chloro- and 2,6-Dichlorothieno[2,3-e][1,4,2]dithiazine 1,1-Dioxides

A series of 3-(alkylthio)-6-chlorothieno[2,3-e][1,4,2]dithiazine 1,1-dioxides (7a - e) were prepared via interaction of deprotonated 2,5-dichlorothiophene-3-sulfonamide with carbon disulfide under reflux, followed by alkylation with alkyl halides. Employment of dimethyl sulfate afforded the isomeric 2-methyl-3-thione derivative 8 together with the expected 3-(methylthio) derivative 7a in a molar ratio of 1 : 4. Treatment of 7a or 10 with ethylamine, aniline or p-chloroaniline produced the corresponding N-ethyl- (or N-phenyl)-6-chlorothieno[2,3-e][1,4,2]dithiazine-3-amine 1,1-dioxides 3a - c. Likewise, interaction of 7a with methylhydrazine (or phenylhydrazine) gave the respective 3-(1-methylhydrazinyl or 2-phenylhydrazinyl) 1,1-dioxides 9a, b. Desulfonation of 6-chloro-3-(methylthio)thieno[ 2,3-e][1,4,2]dithiazine 1,1-dioxide (7a) with sulfuryl chloride produced 3,6-dichlorothieno[2,3- e][1,4,2]dithiazine 1,1-dioxide (10). The latter compound was used as a substrate for the preparation of N-alkyl- (or aryl)-6-chlorothieno[2,3-e][1,4,2]dithiazin-3-amine 1,1-dioxides 3a - c representing a new approach for the synthesis of similar derivatives. Compounds 7a - e showed modest to low antibacterial activity against E. coli and S. aureus. Graphical Abstract Concise Synthesis and Displacement Reactions of Model 3-(Alkylthio)- 6-chloro- and 2,6-Dichlorothieno[2,3-e][1,4,2]dithiazine 1,1-Dioxides