Unsymmetrical trimesogens exhibiting the undulated twist grain boundary (UTGBC*) mesophase

A new set of trimesogens consisting of a cholesteryl ester, a biphenyl and an azobenzene mesogenic segment joined together through either odd-even, even-even or odd-odd central alkylene spacers has been synthesized and the liquid crystalline properties investigated. The trimesogens having even-even and odd-odd central alkylene spacers exhibit the undulated twist grain boundary phase (UTGBC*) mesophase over a temperature range of ~40-50°C.     

Cu–N‐heterocyclic carbene‐catalysed synthesis of 2‐aryl‐3‐(arylethynyl)quinoxalines from one‐pot tandem coupling of o‐phenylenediamines and terminal alkynes

A series of new benzimidazolium chlorides bearing N,N′‐benzyl, 2,4,6‐trimethylbenzyl and 2,4,6‐triisopropylbenzyl substituents have been designed and synthesized from various o‐phenylenediamines. Subsequently, corresponding Cu‐based N‐heterocyclic carbenes (NHCs) were generated in situ in the reaction medium which represents a new application of NHCs exploiting distinct catalytic property towards intermolecular cyclization reaction cascade for the synthesis of 2‐aryl‐3‐(arylethynyl)quinoxalines from o‐phenylenediamines and terminal alkynes. The outcome of the cyclization reaction product depends upon the N,N′‐substituents present on the benzimidazolium chlorides.     

Camphor-10-sulfonamide-based prolinamide organocatalyst for the direct intermolecular aldol reaction between ketones and aromatic aldehydes

Prolinamides derived from l-proline and N,N-dialkyl 2-aminocamphor-10-sufonamides have been synthesized and used as organocatalysts in the direct intermolecular aldol reaction. Reactions of several aromatic aldehydes with cyclohexanone, cyclopentanone, 4-oxa and 4-sulfa-cyclohexanones and acetone are investigated employing 1a as an organocatalyst. Very high to excellent selectivities are obtained in these direct aldol reactions.     

Physikalisch-chemische Vorgänge beim Wachsen von Herpes tonsurans

Ohne Zusammenfassung Deutsch von Alfred Kuhn (Leipzig).     

First examples of monodisperse discotic liquid crystal pentamers: synthesis and mesomorphism

The synthesis and mesomorphism of the first examples of ‘discotic liquid crystal pentamers’ are reported. Structural characterization of these difunctional pentamers has been achieved by FTIR, NMR, and elemental analysis. The mesophase behavior exhibited by these ‘star-shaped’ molecules has been studied by polarizing optical microscopy and differential scanning calorimetry. The columnar hexagonal structure of the mesophase was established with the help of X-ray diffraction studies.     

Experimental studies on the B7 phase of a banana-shaped achiral mesogen

We report optical, X-ray, polarization and response time measurements on a new 'bananas-haped' mesogen. The material has a salicylaldimine segment in the linear part of the core, but is otherwise structurally similar to the mesogen first reported to show a banana mesophase. Textural and X-ray studies show that this mesophase has all the characteristics of the recently discovered B₇ phase. It is observed that the voltage required to obtain electrical switching is quite low compared with values for the few other materials exhibiting the B₇ phase.     

Lewis acid- and/or Lewis base-catalyzed [3+2] cycloaddition reaction: synthesis of pyrazoles and pyrazolines

A facile, InCl₃ and/or DABCO mediated 1, 3-dipolar cycloaddition of ethyl diazoacetate (EDA) with various activated olefins under solvent-free conditions at ambient temperature to afford 3, 5-disubstituted pyrazolines and pyrazoles in moderate to good yields is reported.