Tetrahydrofuran → tert-Butyl 6-[(6-methylpyridin-2-yl)methyl]-1,4-oxazepane-4-carboxylate

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Reaction Steps

0.5M 9-Borobicyclo[3.3.1]nonane in THF (415 mL, 0.21 mol, 1.1 eq) was added under stirring in a stream of argon at room temperature to tert-butyl 6-[(cyclopropylmethoxy)methyl]-6-hydroxy-1,4-oxazepane-4-carboxylate (Preparation 80, 40 g, 0.19 mol, 1 eq). The reaction mixture was stirred at room temperature for 2 h. After this, the catalyst palladium (0) tetrakis(triphenylphosphine) (4 g, 0.003 mol, 0.02 eq) and 2-bromo-6-methylpyridine (36 g, 0.21 mmol, 1.1 eq) were added to the mixture, and the latter was stirred for 15 min. Then 3M potassium carbonate solution (125 mL, 0.38 mol, 2 eq) was added, and the reaction mixture was refluxed for 3 h. The mixture was cooled, diluted with hexane (300 mL) and DCM (100 mL). The organic layer was separated, washed with water (2×100 mL), and with the saturated sodium chloride solution. The combined aqueous layer was extracted with ethyl acetate/hexane (3:1) mixture (2×200 mL). The organic layers were sequentially filtered through silica (25 g; 63-100 μm) and sodium sulphate (50 g) and evaporated. The residue was subjected to chromatography (carbon tetrachloride/chloroform/isopropanol 100:0:0→90:10:0→70:30:0→50:50:0→30:70:0→0:100:0→0:99:1→0:98:2→0:97:3→0:95:5→0:93:7→0:92:8→0:90:10) on silica (500 g; 63-100 μm). The fractions, containing the product, were collected and evaporated to give title compound as a light oil in (42.5 g, 0.14 mol, 74%).

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