Effect of cyclodextrin complexation in bromine addition to unsymmetrical olefins: evidence for participation of cyclodextrin hydroxyl groups

Multiple recognition by cyclodextrin in a bimolecular reaction, namely bromination of styrene, methyl cinnamate, phenylacetylene and allylbenzene, has been studied. Bromohydrin is obtained as a major product along with dibromide in the bromination of styrene and methyl cinnamate. The percentage of bromohydrin decreases as the cavity size increases. With phenylacetylene, bromophenylacetylene and phenacyl bromide are obtained in addition to the dibromides. In the bromination of cyclodextrin complexes of allylbenzene, the product distribution is the same as in solution bromination. The observed results demonstrate the efficiency of cyclodextrin in stabilizing the open carbocationic intermediate and thus provide chemical evidence for the participation of cyclodextrin hydroxyl groups.     

Crystal structure of bis(2-butyl-4-chloro-imidazole)5-iminoethane

The title compound (C₁₈H₂₆N₆Cl₂) crystallizes in monoclinic space group P2₁/c with a = 14.867(4) Å}, b = 7.758(2) Å}, c = 9.671(3) Å}, = 108.78(1), V = 1056.0(5) Å}³, Z = 2, D_cal = 1.250 Mg/m³ at T = 293 K. The structure was solved by direct methods and refined by full-matrix least-squares procedures to final R = 0.0650 and wR = 0.1719 using 2493 reflections. The imidazole ring is planar and the n-butyl chain adopts an extended conformation. The molecules in the crystal are stabilized by N–H s N type of intermolecular hydrogen bondings in addition to van der Waals forces.     

Synthesis and characterization of 9-(4-nitrophenyl)3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione and its methoxyphenyl derivative

9-(4-Nitrophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione (NTHA) crystallizes in orthorhombic space group P2₁2₁2₁ with a = 5.9716(1) Å, b = 18.0476(3) Å, c = 19.2445(2) Å, V = 2074.04(5) ų, Z = 4, D_cal = 1.263 Mg m^?3 and R = 0.0521 (wR = 0.1326) for 4078 observed reflections. 9-(4-Nitrophenyl)-10-(4-methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione NMTHA, crystallizes in monoclinic space group P2₁/c with a = 15.669(5) Å, b = 10.652(4) Å, c = 18.337(6) Å, β = 108.25(1)^°, V = 2906.66(2) ų, Z = 4, D_cal = 1.245 Mg m^?3 and R = 0.0725 (wR = 0.1847) for 5105 observed reflections. The experimental values are compared with the theoretical values calculated based on the semiemperical methods. The structures are stabilized by N–H?sO and C–H?sO types of intermolecular interactions in addition to van der Waals forces.     

Non-coplanar aromatic carboxylic acids: Unusual conformation-dependent self-assembly and pseudopolymorphism of di(3-carboxymesityl)methane

The dicarboxylic acids 3 and 4, i.e., di(3-carboxy-2,4,6-trimethylphenyl)methane and di(3-carboxyphenyl)methane, are created by a methylene tethering of mesitoic acid and benzoic acid, respectively. These diacids may explore two low energy conformations, viz., syn and anti. Whereas the syn-diacid 3 is found to undergo self-assembly in the solid state via a very rare tetrameric motif, the anti-diacid 3 is found to exhibit pseudopolymorphism with guest molecules such as DMSO and PhOH–H₂O. The unusual patterns of assembly and the occurrence of pseudopolymorphism for the syn and anti conformers, respectively, appear to emanate from an unique structural feature that emerges as a consequence of tethering. It appears that the molecules that contain strongly interacting functional groups in non-coplanar aryl rings will suffer from packing problems, which manifests itself in a new mode of packing and the phenomenon of pseudopolymorphism.     

Synthesis of seco-psymberin/irciniastatin A: the discovery of a novel PhI(OAc)2 mediated cascade cyclization reaction

The psymberin unsaturated ‘psymberate’ side chain 7 was synthesized in 7 steps (36% yield) with good diastereoselectivity using commercially available starting material to control the stereochemistry at C₄ and C₅. The synthesis of seco-psymberin was completed in an efficient manner based on a CuI mediated coupling reaction between vinyl iodide 8 and ‘psymberamide’ 7. In an attempt to synthesize natural psymberin from the seco-intermediate, a novel PhI(OAc)₂ mediated cascade ring closing reaction was discovered. A possible mechanistic pathway for the formation of the ring closing product was presented.     

Palladium-Catalyzed C-H Bond Functionalization of Benzo[1,2-b : 4,5-b′]dithiophene-4,8-dione: A One Step Access to 2-Arylbenzo[1,2-b : 4,5-b′]dithiophene-4,8-diones

The reactivity of benzo[1,2-b : 4,5-b′]dithiophene-4,8-dione in Pd-catalyzed C−H arylation was investigated. Using aryl bromides as aryl source in the presence of carbonate bases in 1,4-dioxane, the mono-C2-arylated benzo[1,2-b : 4,5-b′]dithiophene-4,8-diones were regioselectively obtained. This procedure allowed to introduce both electron-rich and electron-poor aryl substituents on the benzo[1,2-b : 4,5-b′]dithiophene-4,8-dione unit. These conditions were also effective for the coupling with 1-bromonaphthalene, 9-bromophenanthrene as well as aryl bromides bearing synthetically useful nitrile, chloro and methoxy substituents. The photophysical properties of representative arylated compounds have been performed by joint experimental and theoretical studies.     

Viscous dissipation effects on heat transfer in flow over an inclined plate

The effects of viscous dissipation are considered for natural convection flow past a semi-infinite inclined plate with variable surface temperature. Velocity and temperature profiles, skin friction, and rate of heat transfer are obtained. The effects of Grashof and Prandtl numbers, inclination angle, exponent in the wall temperature variation law, and viscous dissipation parameter on the flow are discussed. It is shown that the time required to reach steady states increases with increasing Prandtl number of the fluid. In addition, an increase in the plate temperature due to viscous dissipation was found to lead to a rise in the average skin friction and a decrease in the average Nusselt number.     

Crystal structures of 3-[1-Benzenesulfonyl-3-phenylsulfanyl-1H-indol-2-yl]-1-[4-(methyl (I)/methoxy (II) phenyl)]-2-phenyl-propane-1-one

The compounds 3-(1-Benzenesulfonyl-3-phenylsulfanyl-1H-indol-2-yl)-1-[4-methyl (I)/methoxy (II)phenyl)]-2-phenyl-propane-1-one crystallize in triclinic space group P . The details are: compound I a = 11.941(6) ?, b = 12.154(7) ?, c = 13.006(7) ?, α = 63.124(8)°, β = 84.464(9)°, γ = 64.810(8)°, V = 1519.7(14) ?³, Z = 2, D _cal = 1.284 Mg m⁻³, and R = 0.0382 (wR = 0.0978); compound II a = 11.897(6) ?, b = 12.268(6) ?, c = 13.001(7) ?, α = 61.919(8)°, β = 83.480(8)°, γ = 64.676(7)°, V = 1504.0(14) ?³, Z = 2, D _cal = 1.333 Mg m⁻³, and R = 0.0422 (wR = 0.1049). The indole ring system in both the molecules I and II are not strictly planar and the dihedral angles formed by the pyrrole and benzo planes are 4.0(7)° and 3.5(8)°, respectively. The C–HO, C–Hπ and ππ types of interactions stabilize the molecules in the unit cell in addition to van der Waal's forces in I and II.     

Comparison of two different electrophoretic methods in studying the genetic diversity among plantains (Musa spp.) using ISSR markers

Inter simple sequence repeat markers were employed for the genotyping of 16 plantain ecotypes. Two different electrophoretic systems namely conventional gel electrophoresis (CVGE) and fully automated high‐resolution CGE were used to evaluate the genetic diversity. Comparative analysis indicated that all parameters related to marker informativeness were higher in CGE except polymorphic information content. But genetic diversity parameters like effective number of alleles, Nei's gene diversity (1973) and Shannon's information index showed higher values (1.52 ± 0.12, 0.34 ± 0.05 and 0.52 ± 0.05, respectively) in CVGE as against CGE (1.29 ± 0.04, 0.22 ± 0.02 and 0.38 ± 0.03, respectively) system. The unweighed pair group method with arithmetic averages was used to obtain the dendrogram for both analyses. The results of dendrogram and principal component analysis were found to be consistent in both systems except for some minor disagreements. The clone‐specific bands could be used in the identification and development of SCAR markers. Inter simple sequence repeat markers used in this study provided sufficient polymorphism and reproducible banding pattern for evaluating the genetic diversity of different plantain ecotypes. Lack of accuracy and consistency of the CVGE warrants the employment of high‐throughput CGE for diversity analysis as it provided better separation of bands with higher resolution.