Heterocalixarenes. Part 3: Bis-oxo-bridged calix[1]cyclicurea[3]arene and calix[1]cyclicurea[1]pyridine[2]arenes. Synthesis, X-Ray crystal structure and conformational analysis

The Friedel-Crafts aroylations of 2- and 4-methylanisole with isophthaloyl dichloride or pyridine-2,6-dicarbonyl dichloride provide respective diones, which on bromination with NBS provide corresponding bisbromomethyl derivatives that undergo simple cyclocondensations with embedded cyclicurea-containing heterocycles, viz. benzimidazol-2(1H)-one, 5-nitrobenzimidazol-2(1H)-one, 5,6-dinitrobenzimidazol-2(1H)-one, uracil and quinazoline-2,4(1H,3H)-dione to form 11 new bis-oxo-bridged heterocalix[4]arenes ( 11-19, 24, 25). The X-ray crystal structure of the 11-benzene complex, 1H-1H COSY spectra and energy-minimization studies assign partial cone conformations to these heterocalix[4]arenes. The variation in the cyclicurea moiety controls the flexibility of these heterocalix[4]arenes

Heterocalixarenes part 4. Synthesis of oxocalix [1] heterocycle [2]-arenes: a unique H-bonding network in calix [1] benzimidazol-2-one [2] arene &#189; H<SUB>2</SUB>O

The Friedel.Crafts aroylation of 2-methylanisole with 3-methylbenzoyl chloride followed by NBS bromination and cyclizations with 1,3-dihydrobenzimidazol-2-one, 1,3-dihydro-5,6-dinitrobenzimidazol-2-one, uracil, 6-methyluracil and quinazoline-2,4(1H,3H)-dione provide respective oxocalix[1]heterocycle[2]arenes 5.9. The X-ray crystal structure (solid) and 1H NMR spectral (solution) studies show them to have by and large inwardly flattened partial cone conformations which vary in torsion angles between the rings. The calix[1]benzimidazol-2-one[2]arene &#189; H2O complex shows a unique array of H-bonds in which three of the four CH and the imide oxygen of the benzimidazol-2-one unit, carbonyl oxygen and water molecule are involved in H-bonding with surrounding calixarene molecules. This heterocalixarene, in contrast to earlier reported benzimidazol-2-one-based calixarenes, does not show heterocyclic &#960;-&#960; stacking

The synthesis and X-Ray structure analysis of an unusual bent anthraquinone based coronand

The phase transfer catalyzed cyclisation of 1,8-dihydroxyanthraquinone with bis(2-bromoethyl) ether provides an unusual bent anthraquinone based coronand

Synthetic ionophores. Part 18: Ag<SUP>+</SUP> selective trithiabenzena-and dithiabenzenapyridinacyclophanes

The phase transfer catalysed nucleophilic displacement of 1,3-bis(bromomethyl)benzene, 2-methoxy-5- methyl-1,3-bis(bromomethyl)benzene (2) and 1,4-bis(bromomethyl)benzene with 2-mercaptoethanol gives the respective diols 3, 4 and 12 (80-85%), which undergo intermolecular cyclodehydrochlorination with thiodiglycolyl dichloride and pyridine-2,6-dicarbonyl dichloride?HCl to provide m-phenylene (7-10) and p-phenylene (13-14) based crownophanes. The single crystal X-ray structures of crownophanes 8 and 13 and their NMR studies show that the m-phenylene and p-phenylene rings remain in plane and perpendicular to the macrocyclic ring both in solution and solid phases. These crownophanes offer three soft coordinating sites (3 &#215; S or 2 &#215; S and 1 N) conducive to complexation with Ag+ and the steric restrictions imposed by m- and p-phenylene rings restrict 2 :1 (L :M) sandwich complexation required for complexation with the borderline soft Pb2+ cation. The crownophanes 7 and 9 extract Ag+ 172 and 602 times, respectively, more than Pb2+

Heterocalixarenes. 1. Calix [2] uracil [2] arene: synthesis, X-ray structure, conformational analysis, and binding character

1,3-Bis[(1-uracilyl)methyl)]benzene derivatives 3, formed by selective N-1 alkylation of 1,3-bis(trimethylsilyloxy)pyrimidine with 1,3-bis(bromomethyl)benzene derivatives 2, on cyclization with the same or different derivative of 2, provide calix[2]uracil[2]arenes 4. Their conformations, investigated through X-ray, variable temperature 1H NMR, and molecular modeling MM2 calculations, are found to depend on the nature of substituent(s) on the position 2 of 1,3-phenylene rings. 4a exists in equilibrium between various conformations, and 4b, 4d-4i adopt an inward flattened partial cone conformation. In 4j, the equilibrium is restricted to two conformations at -60 &#176;C, but the 4j.ethanol complex (2:1), in the solid state, has a cone conformation with ethanol being a H-bond donor through H of OH and CH2 and an acceptor through O of OH. 4d, 4j, and 4k exhibit significant preferences toward alkaline earth metal ions over alkali metal ions though overall bindings are poor

Copper(II)-Catalyzed Disulfide ScissionStepwise Aerobic Oxidative Cleavage to Sulfinate and Sulfonate and Reductive Anaerobic Cleavage to Thiols

The Cu­(II)-catalyzed oxidative and reductive cleavage of the disulfide bond of <i>N</i>-(2-(2-(2-picolinamido)­phenyl)­disulfanyl)­phenyl)­picolinamide, <b>L</b>, is reported for the first time. Aerobic oxidation with Cu­(II) gives complete oxidation of S–S bond to sulfonates, whereas Ag­(I) gives only partial oxidation up to sulfinates, in the absence of any other oxidizing agent, in tetrahydrofuran/water solution. The <i>in situ</i> generated sulfonate product forms a thermally stable, two-dimensional H-bonded polymeric complex with Cu­(II) ions in two polymorphic forms. <b>L</b> in the presence of Cu­(II), in an inert atmosphere, results in a reductive cleavage of the disulfide bond and an <i>in situ</i> formation of a new C–S bond. The latter forms a unique tetranuclear complex with Cu­(II) employing deprotonated amide groups and bridging thiol and chloride atoms. The disulfide precursor and the products were characterized by X-ray crystallography and spectroscopic techniques

Spontaneous Resolution upon Crystallization of 3D, Chiral Inorganic Networks Assembled from Achiral, Polyoxometallate Units and Metal Ions

Two enantiomerically pure 3D chiral POM-based compounds <b>1a</b> and <b>1b</b>, having formula (H₃O⁺)₂[K₂(SiW₁₂O₄₀)­(H₂O)₄]·H₂O, have been isolated during crystallization. Single-crystal X-ray diffraction analysis revealed that <b>1a</b> and <b>1b</b> are enantiomers, crystallizing in chiral space groups <i>P</i>6₂22 and <i>P</i>6₄22, respectively. The compounds are optically active, and their UV spectra show Cotton effects in the opposite direction. Compounds <b>1a</b> and <b>1b</b> represent the examples of 3D chiral frameworks of POM-based inorganic skeletons, obtained by spontaneous resolution upon crystallization from achiral precursors. The crystal structures represent open frameworks with water molecules in the chiral, nanotubular channels

Synthesis, NMR, X-ray structural analyses and complexation studies of new Ag⁺ selective calix[4]arene based dipodal hosts—a co-complexation of neutral and charged species

New podands based on the p-tert-butylcalix[4]arene unit with substitution at the lower rim incorporating imine units, have been synthesized in high yield by simple condensation method. These podands have been shown to extract and transport Ag+ selectively over alkali, alkaline earth metal cations, Zn2+, Pb2+ and Hg2+ ions, from neutral aqueous phase to organic phase. In all the ligands the calix unit has been found to be present in a cone conformation except for the one having pyridine as end group, at the ortho position. It has been isolated in two conformations; cone and 1,2-alternate. To the best of our knowledge, this may be the first 1,3-lower rim substituted calix[4]arene to exist in a 1,2-alternate conformation and is among a few known compounds with this conformation in the general class of calix[4]arenes. A complex of this ligand, which happens to be the highest extractant of Ag+ has been isolated and characterized using mass, 1H and 13C NMR spectroscopy's and elemental analysis. The spectroscopic evidence and molecular modelling studies performed on the complex suggest a participation of the imine and pyridine nitrogens and two of the ether oxygens in coordination to the metal ion. The X-ray crystal structures of three of the ligands establish the formation of inclusion complexes with polar acetonitrile solvent molecules. The 1H and 13C NMR spectra of all the compounds, taken in CDCl3, show the presence of acetonitrile molecules in the cavity of the calix[4]arene, indicating inclusion of the neutral guest molecules in the solution phase as well. For one of the podands X-ray crystal structure has shown a formation of clatharate complex of chloroform with the ligand which has rarely been found in the case of calix[4]arenes