المنشورات و المؤلفات
The theoretical and experimental vibrational frequencies of 3-(diacetylamino)-2-ethyl-3H-quinazolin-4-one (2) were investigated. The experimental Laser-Raman spectrum (100-4000 cm-1) and FT-IR spectrum (400-4000 cm-1) of the newly synthesized...
Factors affecting reactions of trialkylcyanoborates with imidoyl chlorides/trifluoroacetic anhydride
Methods for generating tert-alkyl organoboron species are in high demand as they are invaluable intermediates for the synthesis of quaternary carbon centres. Herein we report investigations into generation of tert-alkyl organoboron species using...
The photostabilization of poly(vinyl chloride) (PVC) films having five Schiff's bases derived from sulphamethoxazole has been investigated. The casting method was used to produce PVC films containing sulphamethoxazoles (0.5% by weight), in...
The photostabilization of poly(methyl methacrylate) (PMMA) films having 2-(6-methoxynaphthalen-2-yl)propanoate and Sn(II), Ni(II), Zn(II), and Cu(II) complexes was investigated. The production of PMMA films containing such complexes (0.5% by weight...
Traditional Friedel-Crafts acylation reactions of aromatics suffer from low regioselectivity towards para- or more linear isomers and usually require stoichiometric quantities of Lewis acids, which are hydrolysed to produce toxic waste during...
In the title compound, C12H7N3O2S, the dihedral angle between the planes of the thiazolopyridine ring system (r.m.s. deviation = 0.005 Å) and the benzene ring is 3.94 (6)°. The nitro group is rotated by 7.6 (2)° from its attached ring. In the...
In the title compound, C12H14N2S, the cyclohexane ring adopts a chair conformation with the exocyclic C—C bond in an equatorial orientation. The mean plane through the cyclohexane ring (all atoms) is twisted from the thiazolopyridine ring system...
Objectives: To investigate tear ferning (TF) test repeatability between sessions by observing changes in the tear fern pattern during the day.
Methods: Twenty-three healthy young adults (15 men and 8 women), ranging in age from 20 to 32 years (mean±...
The molecule of the title compound, C10H11N3O, is planar, including the ethyl group, as indicated by the N—C—C—C torsion angle of 1.5 (2). In the crystal, inversion-related molecules are stacked along the a axis. Molecules are oriented head-to-tail...
In the title molecule, C11H13N3O, the propyl group is almost perpendicular to the quinazolin-4(3H)-one mean plane, making a dihedral angle of 88.98 (9). In the crystal, molecules related by an inversion centre are paired via p–p overlap, indicated...
In the title molecule, C13H10N2S, the dihedral angle between the planes through the non-H atoms of the methylbenzene and thiazolopyridine groups is 36.61 (5). In the crystal, the thiazolopyridine groups of inversion-related molecules overlap, with a...
There are two molecules in the asymmetric unit of the title compound, C11H16N2O. The pyridine rings and amide groups overlap almost perfectly (r.m.s. overlay fit = 0.053 A˚ ), but the tertiary butyl groups have different orientations: in one...
In the title molecule, C9H10N2S, one of the methyl groups is almost co-planar with the thiazolopyridine rings with a deviation of 0.311 (3) A˚ from the least-squares plane of the thiazolopyridine group. In the crystal, weak C—H....N hydrogen-bonding...
In the title compound, C10H14N2O, the pyridine ring is inclined to the mean plane of the amide moiety [N—C( O)C] by 17.60 (8). There is an intramolecular C—H O hydrogen bond present involving the carbonyl O atom. In the crystal, molecules are...
Directed lithiation of substituted pyridines containing a directing metalating group (DMG) with a lithium reagent in anhydrous solvent at low temperature gives the corresponding lithium intermediates in-situ, which on reactions with electrophiles...
Five new thiophenes, namely N-[(3-bromo-2-methylthiophen-5-yl)methylene]-4-methoxyaniline (4a), N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethoxyaniline (4b), N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethylaniline (4c), 3-[(3-...
Highlights
•The Masmali five-point tear ferning grading scale was applied on non-dry and dry eye.
•The validation of the grading scale was tested in practice.
•Grades ≥2 can be considered as dry eye.
•The Masmali TF grading scale showed good...
The title compound, C9H8N2O, is almost planar, with the C atom of the methoxy group deviating from the mean plane of the quinazoline ring system (r.m.s. deviation = 0.011 A˚ ) by 0.068 (4) A˚ . In the crystal, molecules form – stacks parallel to the...
The present work focuses on the development of a novel computer-based approach for tear ferning (TF) featuring. The original TF images of the recently developed five-point grading scale have been used to assign a grade for any TF image automatically...
Two cyclic and two polymeric disulfides have been synthesized and established to be useful catalysts for the chlorination of m-xylenol, o-cresol, m-cresol and phenol using freshly distilled sulfuryl chloride in the presence of aluminum or ferric...
Condensation of 6-bromo- and 6,8-dibromo-2-hydrazino-3-phenyl-3H-quinazolin-4-ones with d-sugars in the presence of a catalytic quantity of glacial acetic acid gave the corresponding hydrazones in good yields. Acetylation of hydrazones with acetic...
Directed lithiation of substituted aromatics and heterocycles containing a directing metalating group with alkyllithium in anhydrous tetrahydrofuran or diethyl ether at low temperature provides the corresponding lithium intermediates. Reaction of...
Lithiation of N'-(2-methylphenyl)-N,N-dimethylurea with three molar equivalents of tert-butyllithium at -40 to -30 °C takes place on the nitrogen and on the methyl group at position 2 of the phenyl group. The lithium intermediate thus obtained...
In the molecule of the title compound, C17H16N2OS, the almost planar methylsulfanylquinazoline group [the methyl C atom deviates by 0.032 (2) A˚ from the plane through the ring system] forms an interplanar angle of 76.26 (4) with the plane of the...
In the title compound, C22H28N2, the dihedral angle between the planes of the phenyl ring and the dihydroquinazoline ring system (r.m.s. deviation = 0.030 A˚ ) is 24.95 (7) and both n-butane chains assume all-trans conformations. In the crystal, N—H...
In the title compound, C17H27N3OS2, the amide group is approximately coplanar with the pyridine ring [dihedral angle = 1.6 (1)], whereas the dithiocarbamate group is nearly perpendicular to the pyridine ring [dihedral angle = 76.7 (1)]. In the...
Nitration of 2-nitrotoluene using nitric acid, acetic anhydride and Hβ zeolite produces a 97% yield of 2,4-dinitrotoluene along with 3% of 2,6-dinitrotoluene. Nitration of 4-nitrotoluene under similar reaction conditions produces 2,4-dinitrotoluene...
In the title compound, C10H10N2S, all non-H atoms are almost coplanar [maximum deviation = 0.103 (1) A ° ]. In the crystal, N—H S interactions form R22(8) rings linking pairs of molecules related by inversion. The molecular pairs are stacked along...
The title compound, C10H12N2S, does not contain any strong hydrogen-bond donors but two long C—H ...... N contacts are observed in the crystal structure, with the most linear interaction linking molecules along [010]. The ellipsoids of the tert-...
In the title compound, C15H12N2S, the methylthioquinazoline group is planar with the methyl C displaced by only 0.116 (3) A˚ from the plane of the quinazoline moiety. The dihedral angle between the phenyl ring and the quinazoline ring system is 13....
In the title compound, C9H10BrClN2S, the dimethylthiourea group is twisted from the benzene ring plane by 54.38 (6). In the crystal, the amino groups are involved in the formation of N—HS hydrogen bonds, which link the molecules into chains along [...
The spectroscopic properties of (E)-3-(4-bromo-5-methylthiophen-2-yl)acrylonitrile have been investigated by FT-IR, UV, 1H and 13C NMR techniques. The theoretical vibrational frequencies and optimized geometric parameters (bond lengths and angles)...
AbstractObjectives:
To investigate the repeatability of the phenol red thread (PRT) and Schirmer’s tests in healthy Saudi adults. Additionally, we compared the PRT mean value with those reported previously, because of significant differences between...
In the title compound, C20H21N3O2.H2O (EQR.H2O), the quinazoline ring system forms dihedral angles of 53.1 (1) and 85.6 (1)o with the phenyl ring and the amide link, respectively. In the crystal, O—H...O hydrogen bonds link two EQR and two water...
In the title compound, C11H16N2O, the dihedral angle between the mean plane of the 4-methypyridine group and the plane of the amide link is 16.7 (1)° and there is a short intramolecular C5—H5•••O1 contact. Hydrogen bonding (N—H•••O) between amide...
Abstract:
Various nitration systems comprising nitric acid, acid anhydride and zeolite Hβ in the absence of solvent are described. Direct double nitration of toluene over a nitric acid, propanoic anhydride and zeolite Hβ system has been developed to...
Objectives:
To investigate the repeatability and average tear osmolarity using the new lab-on-chip TearLab technology device in normal subjects living in Saudi Arabia, a hot climate country, and to compare the average readings with data from...
2-(3-(tert-Butoxycarbonylamino)propyl)-5-methylthiophene and its 4-deuterio derivative have been synthesized by a simple and convenient method in a six step sequence from 2-methylthiophene. The final step involved bromine-lithium exchange on 4-bromo...
Diphenyl (4'-aminobiphenyl-4-ylamino)(pyridin-3-yl)methylphosphonate (1) was synthesized in 88% yield from reaction of pyridine-3-carboxaldehyde with benzidine and triphenylphosphite in the presence of titanium tetrachloride as a catalyst....
The crystal structure of the title compound, C26H39BO2, which contains no strong hydrogen bond donors, displays only long C-HO contacts between inversion-related pairs of molecules. The structure contains layers rich in oxygen and boron parallel to...
The crystal structure of the title compound, C29H16F6N2S2-0.5 CHCl3, consists of molecules with disordered perfluorocyclopentene rings [occupancy ratio 0.685 (3):0.315 (3)] and close F...F contacts (in the range 2.45–2.73 Å) between molecules. The...
Lithiation of N-(pyridin-3-ylmethyl)pivalamide, tert-butyl N-(pyridin-3-ylmethyl)carbamate and N'-(pyridin-3-ylmethyl)-N,N-dimethylurea with three mole equivalents of t‑butyllithium in anhydrous THF at -78 °C takes place on the nitrogen and on the...
Series of diphenyl 1-(arylamino)(pyridin-3-yl)methylphosphonates were obtained in high yields from the reactions of nicotinaldehyde with aromatic amines and triphenylphosphite in the presence of titanium tetrachloride as a catalyst. The structures...
A V-ATPase subunit A protein (VHA-A) transcript together with a variant (C793 to U), which introduces a stop codon truncating the subunit immediately downstream of its ATP binding site, was identified within a Fucus vesiculosus cDNA from a heavy...
In the title compound, C19H21ClN2O2, the aromatic rings are approximately perpendicular to each other, subtending a dihedral angle of 87.7 (1)°. In the crystal, the 4-nitrophenyl groups of pairs of neighbouring molecules are parallel and oriented...
We have investigated the dinitration of toluene over zeolite under various reaction conditions with the aim to produce 2,4-DNT selectively and in high yield. The best result obtained under produce 2,4-DNT in 90%. Therefore, in an attempt to push the...
N'-(2-(4-Methoxyphenyl)ethyl)-N,N-dimethylurea and tert-butyl (2-(4-methoxyphenyl)ethyl)carbamate are doubly lithiated on the nitrogen and ortho- to the directing metalating group at -20 to 0 °C with three mole equivalents of n-BuLi in anhydrous THF...
Our research has been oriented towards the development of greener processes for the synthesis of commercially important products, especially in the area of selective electrophilic aromatic substitution reactions, which are of major industrial...
A nitration system comprising nitric acid, propanoic anhydride and zeolite Hb has been developed for dinitration of toluene to give 2,4-dinitrotoluene in 98% yield, with a 2,4-:2,6‑dinitrotoluene ratio of over 120. This represents the most selective...
In the title structure, C8H6BrNS, the molecules are planar with the exception of the methyl H atoms. In the crystal, molecules are linked by intermolecular C—HN interactions to form ribbons parallel to the b axis. Groups of ribbons are arranged in a...
Lithiation of N-(2-(4-methoxyphenyl)ethyl)pivalamide at -20 to 0 °C with three mole equivalents of n-BuLi in anhydrous THF, followed by reactions with various electrophiles, gives high yields of products involving ring substitution ortho- to the...