Benzenesulfonic acid, 4-methyl-, compd. with pyridine (1:1) → 2-(3-Cyclopentyloxy-4-methoxybenzyl)-7-nitrobenzoxazole

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A solution of N-(2-hydroxy-3-nitrophenyl)-3-cyclopentyloxy-4-methoxyphenylacetamide (2.0 g) and pyridinium p-toluene-sulphonate (500 mg) in xylene (140 ml) was refluxed, under nitrogen, overnight. The reaction mixture was cooled to room temperature, diluted with water (100 ml) and extracted with dichloromethane (3×75 ml). The combined organic extracts were washed with water (3×100 ml), brine (100 ml), dried (CaSO4) and evaporated in-vacuo to yield an orange oil. The oil was purified by flash chromatography (SiO2 ;dichloromethane;ethanol;ammonia (50:1:0.1)) to yield the title compound (1.107 g, 58%) as an orange solid (top 95°-98.5° C.). δH (250 MHz;d6DMSO) 1.45-1.95 (8H,m,4×CH2), 3.70 (3H,s,OMe), 4.36 (2H, s,CH2), 4.74 (1H,m,CH), 6.89 (2H,bs,ArH), 7.02 (1H,bs,ArH), 7.56 (1H,t,ArH), 8.15 (1H,dd,ArH), 8.17 (1H,dd,ArH). m/z 368 (M+), 338 (M--NO), 300 (M--C5H8), 285, 270, 253, 149, 137, 123, 100.

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