Hosanagara N. Harishkumar

Synthesis and Liquid Crystal Property of New Fluoro Coumarin Carboxylates

New liquid crystalline 4-alkoxyphenyl-coumarin-3-carboxylates 6a–e, 7a–g, 8a–e, and 9a–e were prepared by reacting various coumarin-3-carboxylic acids 5a–d with 4-(alkoxy) phenols 4a–g in the presence of 1(3-dimethylaminopropyl-3-ethylcarbodiimide/dimethyl amino pyridine (EDCI/DMAP) as a coupling agent. The structures of the new coumarin derivatives were confirmed by spectral analysis and the liquid crystalline property was established by polarizing optical microscope and by differential scanning calorimetric techniques. The diethyl amine and morpholine were taken as electron-donating and –CF3 as electron-withdrawing groups at the seventh position of the coumarin-3-carboxylic acids to check the mesomorphic property in all new 4-alkoxyphenyl-coumarin-3-carboxylates. Among them, only 4-alkoxyphenyl-7-triflouromethyl-coumarin-3-carboxylates 7a–g exhibited liquid crystalline SmA phase.

4-[4-(Hept­yloxy)benzo­yloxy]phenyl 2-oxo-7-tri­fluoro­methyl-2H-chromene-3-carboxyl­ate

The title compound, C31H27F3O7, is a liquid crystal and exhibits enantiotropic SmA and nematic phase transitions. In the crystal, the the 2H-chromene ring system makes dihedral angles of 54.46 (17) and 7.79 (16)°, respectively, with the central benzene ring and 4-(heptyloxy)benzene ring. The three F atoms of the –CF3 group are disordered over two sets of sites, with an occupancy ratio of 0.62 (3):0.38 (3). The crystal structre features two pairs of C—H⋯O hydrogen bonds, which form inversion dimers and generate R 2 2(10) and R 2 2(30) ring patterns. C—H⋯O interactions along [100] and C—H⋯π interactions futher consolidate the packing, leading to a three-dimensional network.

Synthesis of Benzo[b]thiophene Substituted Carbamates, Ureas, Semicarbazides, and Pyrazoles and Their Antimicrobial and Analgesic Activity

2-Azidocarbonyl-3-chlorobenzo[b]thiophene 3 was obtained from 3-chloro-benzo[b]thiophene-2-carbonyl chloride 1 and 3-chloro-benzo[b]thiophene-2-carboxy hydrazide 2 . The compound 3 on Curtius rearrangement with various alcohols, amines, and hydrazines afforded the corresponding carbamates 4a–b , ureas 5a–j , and semicarbazides 6a–g , respectively. Compound 2 was also utilized for the synthesis of pyrazoles 7a–c by treatment with various chalcones. The structures of the newly synthesized compounds were elucidated on the basis of IR, 1 H NMR, and mass spectral data and have been screened for antimicrobial and analgesic activities.

Synthesis and Fluorescence Study of Some New Blue Light Emitting 3-(1,3-benzothiazol/benzoxazol-2-yl)-2H- chromen-2-ones

The synthesis and fluorescence efficiency of 3-(1, 3-benzothiazol/benzoxazol-2-yl)-2H-chromen2-one derivatives 4a-j have been described. To improve the fluorescence characteristics especially emission wavelength, the substitution like diethylamino, fluoro, bromo, chloro, trifluoromethyloxy, methyloxy and methyl groups on 7th position of salicyladehydes 1a-j and substitutions such as fluoro, methyl and nitro groups on 5th and 6th position of ethyl-1,3benzothiazol/benzoxazole-2yl-acetates were selected as donor and acceptor groups. The fluorescence property was investigated spectrophotometrically in chloroform at 1⇥10 6 M concentration with Rhodamine B as standard dye. All the compounds were found to emit blue light in the region between 450 to 495 nm. The quantum yield of all the compounds 4a-j were found to be moderate when compared to Rhodamine B as standard.

3-(2-Bromo­acet­yl)-6-fluoro-2H-chromen-2-one

The non-H atoms of the title compound, C11H6BrFO3, are essentially coplanar (r.m.s. deviation for all non-H atoms = 0.074 Å). In the crystal, the molecules are linked by C—H⋯O and C—H⋯Br interactions.