Showing papers by "Senthamaraikannan Kabilan published in 2004"

Synthesis and Study of Antibacterial and Antifungal Activities of Novel 1-[2-(Benzoxazol-2-yl)ethoxy]-2,6-diarylpiperidin-4-ones.

Abstract: Some novel benzoxazolylethoxypiperidones have been synthesized and their antibacterial activity against streptococcus faecalis, bacillus subtilis, escherichia coli, staphylococcus aureus aand pseudomonas aeruginosa and antifungal activity against Candida-6, Candida albicans, Aspergillus niger, Candida-51 and Aspergillus flavus were evaluated. Compounds 37, 38 and 39 exerted potent in vitro antibacterial activity against Streptococcus faecalis while compounds 40 and 41 exhibited potent in vitro antifungal activity against Candida-51.

Synthesis of some benzoxazolylethoxypiperidones

Abstract: l-Hydroxy-2,6-diarylpiperidin-4-ones obtained from the corresponding 2,6-diarylpiperidin-4-ones upon cyanoethylation followed by condensation with o-aminophenol afforded l-[2-(benzoxazol-2-yl)ethoxy]-2,6diarylpiperidin-4-ones. 2,6-Disubstituted piperidines form a biologically important class of compounds due to their diverse pharmacological activities such as sedative, hypotensive, stimulant and depressant activities etc. and their presence in a variety of alkaloids(l-4). Benzoxazole and its derivatives have been reported to be antibacterial (5), analgesic (6), antifungal (7), activities etc. Antiinflammatory activity of benzoxazole nucleus was well established by the advent of a new antiinflammatory drug benzoxaprofen (8). Medicines derived from oxazole includes the antiepileptic drugs trimethadione and paramethadione (9), the sedative and muscle relaxant benzoxazolamine (9) and furazolidone (10), which is effective against wide range of enteric infections. These observations prompted us to synthesize a system, which combines both biolabile piperidines, and benzoxazole components together to give a compact structure like title compounds. Cyclic ketones normally undergo Baeyer-Villiger oxidation (oxygen insertion reaction) to yield lactones by the treatment of peracids (11). When 2,6-diarylpiperidin-4-ones were subjected to Baeyer-Villiger type of reaction by using /m-CPBA, l-hydroxy-2,6-diarylpiperidin-4-ones (12) resulted instead of lactones. On treatment with acrylonitrile, substituted tetrahydrothiapyran-4-ones containing active hydrogen underwent cyanoethylation yielding 3-[2cyanoethoxy]derivatives (13). In l-hydroxy-2,6-diarylpiperidin-4-ones, there are active methylenic hydrogens at C3 and C5. Hence expectation of cyanoethylation to occur at these positions besides at 1-hydroxyl group is quite normal. However in all the cases, specifically the 1-hydroxy group alone underwent cyanoethylation in good yields (60-74%) upon treatment with acrylonitrile in the presence of triton Β, which on further condensation with o-aminophenol in acid medium resulted l-[2-(benzoxazol-2-yl)ethoxy]-2,6-diarylpiperidin-4-ones in moderate yields. The schematic representation and the analytical data of compounds 34-42 are given in scheme 1 and table 1 respectively. EXPERIMENTAL TLC was performed to access the reactions and purity of products. Melting points were recorded in open capillaries and were uncorrected. IR spectra were recorded in Perkin Elmer 297 spectrophotometer in KBr pellets and only noteworthy absorption levels (reciprocal centimeter) are listed. *H NMR spectra were recorded at 400 MHz on Brucker amx 400 MHz spectrophotometer in CDC13 using TMS as internal standard and C-NMR spectra were recorded at 125 MHz on Brucker amx 400 MHz spectrophotometer in CDC13. Mass spectra were recorded on a VG

Chlorination of N -Phenylbenzenesulfonamides with NCP in Aqueous Acetic Acid. Using the para / meta Ratio of Substituent Effects for Mechanism Elucidation

Abstract: Rate constants were measured for the oxidative chlorination reaction of N -phenylbenzenesulfonamide 2 and twelve ortho -, nine meta - and twelve para -substituted derivatives in the aniline moiety, using 1-chloro-3-methyl-2,6-diphenylpiperidin-4-one ( 1 ) as chlorinating agent. The kinetics was run in 50% (v/v) aqueous acetic acid acidified with perchloric acid under pseudo-first-order conditions with respect to 1 at five different temperatures between 298 and 318 K. The dependence of rate constants on temperature was analysed in terms of the isokinetic relationship (IKR). The resulting isokinetic temperature was estimated to be 513 K. Using the Linert's theory of the IKR, the experimental isokinetic temperature was interpreted as evidence for the preferential involvement of water molecules in the formation of activated complexes. The dependence of the rate constants on the substituents was analysed using the tetralinear extension of the Yukawa-Tsuno equation for the effects of meta and para substituents. A positively charged transition state was suggested by an experimental value r + = 0.39 for the resonance demand, which was found to be insensitive to temperature variation. The parameter λ for the para / meta ratio of substituent effects was estimated to be 0.952. The electrostatic modelling of λ values was re-examined in the light of the recent calculations of the energies of interaction between charged and/or dipolar groups by Exner and Bohm. Based on energy ratios, the electrostatic method was shown to remain valid for the purpose of modelling λ values. The experimental λ value for the reaction indicates the formation of an activated complex possessing an electric charge in the vicinity of the nitrogen atom of the substrate. The electrophilic attack on the substrate nitrogen atom by the protonated chlorinating reagent has been proposed as the rate-determining step, with the last step being the fast rearrangement of the intermediate N -chloro- N -phenylbenzenesulfonamidium cation into the products.

A Convenient Synthesis of Novel 1‐[2‐(Benzimidazol‐2‐yl)ethoxy]‐2,6‐diarylpiperidin‐4‐ones.

Abstract: Upon the study of biological evaluation of benzazolylethoxypiperidones, an array of novel benzimidazolylethoxypiperidones were synthesized. 2,6‐Diarylpiperidin‐4‐ones upon strategical N‐hydroxylation, cyanoethylation followed by acid aided condensation with o‐phenylenediamine afforded a convenient route to novel 1‐[2‐(benzimidazol‐2‐yl)ethoxy]‐2,6‐diarylpiperidin‐4‐ones.