Directed lithiation of simple aromatics and heterocycles for synthesis of substituted derivatives محمد بطاح الشمري
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 the lithium reagents obtained in situ with various electrophiles gives the corresponding substituted derivatives in high yields. The process has been applied for various derivatives and has proven to be a convenient method for modification of ring systems. This brief review highlights the importance of directing metalating groups in directed lithiation of simple aromatic compounds and some common heterocycles as a tool for regioselective substitution.
Crystal structure of 4,4-dibutyl-2-phenyl-3,4-dihydroquinazoline محمد بطاح الشمري
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 N hydrogen bonds link the molecules into C(4) chains propagating in the  direction
Crystal structure of 2-ethylquinazoline-4(3H)-thione محمد بطاح الشمري
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 long . A herringbone arrangement of pairs in the  direction forms layers parallel to (010).
Crystal structure of 4-methoxyquinazoline محمد بطاح الشمري
The title compound, C9H8N2O, is almost planar, with the Catom 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 b-axis direction [centroid–centroid separation =3.5140 (18) A ˚ ], leading to a herringbone packing arrangement.
Comparison of cyclic and polymeric disulfides as catalysts for the regioselective chlorination of phenols محمد بطاح الشمري
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 chloride as a co-catalyst at room temperature. The yields of p-isomers and para/ortho ratios were higher compared to cases where no catalyst was used with most catalysts for most phenols even when a very low concentration of disulfide was used.
4-Methylsulfanyl-2-phenylquinazoline محمد بطاح الشمري
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 13.95 (5). In the crystal, each molecule is linked by – stacking between to two adjacent inversion-related molecules. On one side, the inverted quinazoline groups interact with a centroid–centroid distance of 3.7105 (9) A ˚ . On the other side, the uinazoline group interacts with the pyrimidine and phenyl rings of the second neighbour with centroid–centroid distances of 3.5287 (8) and 3.8601 (9) A ˚ , respectively.
Direct Partial Modal Approach For Solving Generalized First Order Control Systems ايهاب احمد السيد ابوالحمد
Effects Of Thermal Radiation And Viscous Dissipation On MHD Viscoelastic Free Convection Past A vertical Isothermal Cone Surface With Chemical Reaction, ايهاب احمد السيد ابوالحمد
The Partial Eigenvalue Assignment For Non-Symmetric Quadratic Pencil In Multi-Input Case, International Journal of Physical ايهاب احمد السيد ابوالحمد
A Projection Algorithm For Partial Eigenvalue Assignment Problem Using Implicitly Restarted Arnoldi Method, ايهاب احمد السيد ابوالحمد