Synthesis of new crown analogs derived from bisphenol

656-66

Synthesis of crown analogs derived from bisnaphthol

348-35

Cancellation of Contact Quenching : A Simple Concept for Selective Chemosensing of Basic Fluoride and Acetate Anions

A weakly fluorescent acid-base pair formed by reacting fluorescent acridine orange with the quencher picric acid is reported for the detection of basic fluoride and acetate anions. Deprotonation by these anions causes disengagement of the fluorescent acridine orange from the quencher, picric acid. This phenomenon cancels the quenching existing in the native probe, thereby allowing for the optical signalling of fluoride and acetate anions by color modulation as well fluorescence switch-on response. Anions such as Br-, I-, Cl-, NO3-, SCN-, HSO4-, and H2PO4- offer no detectable interferences even in excess concentrations

Synthesis of macrocycles derived from vanillin and isovanillin

5-10Readily available vanillin 1 and isovanillin 2 have been exploited for the first time to synthesise thia and aza-bridged macrocycles. Utilising a common approach, 1 and 2 are first converted into the corresponding key intermediates, dicholoro compounds 5 and 10. Cyclocondensations of these molecules with Na2S under high di lution provide thia-bridged macrocycles 6 and 11 and with p-toluenesulphonamide under basic condition, the aza- bridged macrocycles 7 and 12, respectively are obtained. The structures are fully supported by elemental analysis, mass and high resolution NMR data. Variable NMR measurements on 6 and 11 suggest that these macrocycles are conformationally mobile even at -55°C on the NMR time scale

Attempt towards [2,2](2,4) anti-thiazolophane: Synthesis and conformational analysis of the key intermediate bislactone-bridged thiazolophane

127-131Using the Mukaiyama's protocol, compound 11 is successfully assembled via lactonization of hydroxy acid 9. On the basis of dynamic 1H NMR analysis, thiazolophane 11 is found to be a conformationally mobile system. Unfortunately, the conversion of 11 to the title heterophane 2 could not be realized under either photochemical or thermal conditions

<span style="font-size:12.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-ansi-language: EN-IN;mso-fareast-language:EN-IN;mso-bidi-language:AR-SA" lang="EN-IN">Synthesis of <i style="mso-bidi-font-style:normal">anti</i>-[2.2](2.6)benzothiazolophane via 10π-10π: coupling protocol</span>

959-961<span style="font-size:12.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">The known 6-methoxymethyl-2-methylbenzothiazole 6 has been converted into quaternary ammonium hydroxide <b style="mso-bidi-font-weight: normal">4 via demethoxy-bromination followed by quaternization with (CH3)3N and treatment with silver oxide. Pyrrolysis of <b style="mso-bidi-font-weight: normal">4, expected to generate both anti-1 and <i style="mso-bidi-font-style: normal">syn-[2.2](2.6) benzothiazolophane <b style="mso-bidi-font-weight: normal">2 via 10π-10π &nbsp;couplings of the quinodimethane intermediate 5, gives in practice only anti-benzothiazolophane 1. The structure has been established by comparison with an authentic sample of 1 recently synthesized by an unambigous route.</span

Donor–acceptor thieno[2,3-b]thiophene systems: synthesis and structural study of 3-anisyl-4-pyridyl(pyridinium) thieno[2,3-b]thiophenes

Synthesis of a new class of cofacially oriented neutral donor–acceptor thienothiophene, namely 3-anisyl-4-pyridyl thieno[2,3-b]thiophenes 7 and its ionic analog 8 has been described to probe the presence of through-space charge transfer interaction. However, structural studies by 1H NMR and UV–visible data indicate at best rather weak charge transfer interaction. The single crystal X-ray analysis of the ionic donor–acceptor thienothiophene 8 reveals many interesting features, i.e. (i) the donor and acceptor rings are not parallel to each other (ii) the interchromophoric distance is much larger (4.08 Å) than the van der Waals distance and (iii) the torsional angle between the pyridinium ring and the thienothiophene is unusually small, being only 38°. These structural features preclude effective through-space charge transfer interaction in 8. Conformational analysis of a model system, 3,4-diphenyl thienothiophene indicated that conformations with reduced torsion between the phenyl rings and the thienothiophene plane are possible to maintain a balance between conjugation and steric congestion and the calculated low energy barrier between the high and low energy conformations of the model system suggest the possibility of aryl ring rotations in peri disubstituted thienothiophenes.

Synthesis, optical spectral studies of photoemmitive benzopyranone crown ether and its application for metal ion extraction

1269-1273Synthesi<span style="color: #151515;mso-bidi-language:HI">s <span style="color:black;mso-bidi-language: HI">of a new photoemmitive<span style="color:#151515;mso-bidi-language: HI">, benzopy<span style="color:black; mso-bidi-language:HI">ranone 15-crown-5 (1) has been reported starting from 2-formyl benzo-15- crown-5 by us<span style="color:black; mso-bidi-language:HI">ing a straightforward protocol. Metal ion extractio<span style="color:black; mso-bidi-language:HI">n profil<span style="color:#151515;mso-bidi-language: HI">e revealed 1 to extract K+ more selectively ov<span style="color:black; mso-bidi-language:HI">er N<span style="color:#151515;mso-bidi-language: HI">a+ and Li+ compared to the known benzo-15-crown-5. However, e<span style="color:black; mso-bidi-language:HI">xcept f<span style="color:#151515;mso-bidi-language: HI">or slight enhancements (8 to 27<span style="color:#151515; mso-bidi-language:HI">%) <span style="color:black;mso-bidi-language: HI">in the emission inten<span style="color:#151515;mso-bidi-language: HI">sities, no appreciable changes either in the absorption or emission spectra of 1 were noticeable in the presen<span style="color:#151515;mso-bidi-language: HI">ce of se<span style="color:black; mso-bidi-language:HI">lected group I and II metal ions. The absence of significant optical perturbations <span style="color:#151515; mso-bidi-language:HI">suggests at best only weak interaction between the metal ions and the benzopyranone chromophore<span style="color:#151515; mso-bidi-language:HI">. </span

Novel bipolar diaryloxadiazole-benzofuran conjugates: Synthesis, optical, electrochemical and thermal studies

368-373<span style="font-size:9.0pt;mso-bidi-font-size: 8.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">A series of diaryloxadiazole chromophores incorporating benzofuran rings of varying donor characters has been readily synthesized in a one step protocol. These donor-acceptor-donor systems, designated as <b style="mso-bidi-font-weight: normal">Benzmox-1-4 exhibit positive solvatochromic behavior and thermal stabilities in excess of 300°C. From cyclic voltammetry and emission band data, the HOMO and LUMO energies of Benzmox-1-4 have been calculated to be in the range of 6.43 to 5.65 eV and 2.96 to 3.29 eV, respectively. Of the four chromophoric systems studied, Benzmox-2 and<span style="mso-bidi-font-weight: bold"> Benzmox-3 display band gaps of 3.22 and 3.16 eV, and high luminescence efficiency of 0.34 and 0.55, respectively. These features make Benzmox-2 and<b style="mso-bidi-font-weight: normal"> Benzmox-3 promising bipolar blue light emitting host materials.</span

Synthesis and structures of thieno[2,3-b]thiophene incorporated [3.3]dithiacyclophanes. Enhanced first hyperpolarizability in an unsymmetrically polarized cyclophane

Dithiacyclophanes incorporating thieno[2,3-b]thiophene have been synthesized. in order to investigate the nonlinear optical properties of donor-acceptor cyclophane 7. Cyclophane 7 displayed significantly higher first hyperpolarizability beta (21.6 x 10(-30) esu) compared to model 10 (9.58 x 10(-30) esu). Relatively higher in 7 presumably arises from an extra electron redistribution arising from through-space charge transfer, a feature lacking in 10. Moreover. the thermal decomposition temperature of 7 (300 degrees C) is higher than that reported for the NLO prototype DAN (295 degrees C). (c) 2006 Elsevier Ltd. All rights reserved