4. Experimental Procedure
4.1. General Information
All chemicals were obtained from Sigma-Aldrich or specterochem and used as received. All solvents were distilled using standard methods before use. All reactions were carried out in flame-dried glassware, under a dry nitrogen atmosphere.TLC were performed using TLC silicagel 60 F254 commercially available from Merck (Darmstadt, Germany) using aluminium sheets. 1H-NMR spectra were recorded on a Bruker WM 300 instrument (Milano, Italy) on samples dissolved in CDCl3. Chemical shifts are given in parts per million (ppm) from tetramethylsilane as the internal standard (0.0 ppm). All products in this report are known and were characterized by standard techniques (1H- and 13C-NMR, MS) and the data were compared with those reported in the literature for identification
4.2. WORK DONE
Condensation of o-phenylenediamine5 (OPDA) (1) with 6-fluoro-3,4-dihydro-2i7- chroman-2-eafboxlic acid (2) was done by refluxing 4N hydrochloric acid for 4 hr (Scheme-1), followed by simple work-up yielded a colorless compound, which was found to be homogeneous on TLC and was recrystallised from hot aq. ethanol to give a colorless crystalline compound with a melting range of 232-235°C and in 85% Yield.
Alkylation of (3) with methyliodide and potassium carbonate was done under phase transfer catalysis (PTC) condition by the use of triethylbenzylammonium bromide in refluxing acetone to yield the N-methylatedderivative 2-(6-fluorochroman-2-yl)-1 -methyl- lH-benzimidazole.Similarly, the alkylation was further extended with ethyl iodide, propyl bromide and butyl bromide to yield the corresponding N-alkylated derivatives i.e.,l-ethyl-2-(6- fluorochroman-2-yl)-1-benzimidazole (4b), 2-(6-fluorochroman-2-yl)-l-propyl-l-7-benzimidazole (4c), 1-butyl- 2-(6-fluorochroman-2-yl)-1-benzimidazole (4d).
The reaction of (3) with ethyl and te/t-butyl chloroformatewas done in presence of pyridine as a base yielding the corresponding N-substituted derivatives, ethyl 2-(6-fluorochroman-2-yl)-lH- benzimidazole-l-carboxylate (4e) and tert butyl 2-(6-fluorochroman-2-yl)- lf/-benzimidazole-1 – carboxylate (4f).
4.3. Synthesised Compounds from scheme 2 & 3
Compound (3- 4f)
To the solution of compound (3) (2mmole) in pyridine (5ml) was added slowly and respective acyl or arylsulfonyl chloride at 0 ?C.After the addition was completed, the temperature of reaction mixture was allowed to maintain at room temperature and solution was allowed to stirred at this temperature for 2hr. TLC (Thin layer chromatography) was monitored at regular intervals. A solution of 2N HCl was then added with reaction mixture .Solid product was obtained then it was filtered ,washed with water and dried under vaccum to obtain correspond N-substituted dtv 4e-j respctively.the crude compound were recrystallized from hot aq. ethanol to obtain pure products.
4.4. Synthesised Compounds by scheme 4:
Compound 4g- 4j
The alkylation reaction was explored between compound (3) and benzyl bromide in presence of 5% aqueous sodium hydroxide solution in presence of acetonitrile yielding the N-benzylated products i. e., 1-benzyl-2-(6-fluorochroman-2-yl)-1H benzod imidazole (4k), 1-(3-fluorobenzyl)-2-(6-fluorochroman-2-yl)-1H-benzod imidazole (4l) ,1-(3- bromobenzyl)-2-(6- fluorochroman-2-yl)-1H-benzod imidazole (4m), 2-(6- fluprochroman-2-yl)-1-(3- methylbenzyl)-IH- benzod imidazole (4n), 1-(3-(tert–butyl)benzyl)-2-(6-fluorochroman – 2-yl) – 1H- benzod imidazole (4o).
4.5. Synthesised compounds from Scheme 5: