[4-(4-Cyanophenyl)but-3-ynyl]carbamic acid tert-butyl ester → [4-(4-Cyanophenyl)butyl]carbamic acid tert-butyl ester

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A suspension of [4-(4-cyanophenyl)but-3-ynyl]carbamic acid tert-butyl ester 56 (5.2 g, 19.2 mmol) and 10% palladium on carbon (2.5 g, wet) in ethanol/THE (30 mL, 1:1) was stirred overnight under 1 atmosphere of hydrogen. After purging with nitrogen, the reaction mixture was suction filtered through a pad of Celite. The solvent was removed from the filtrate by evaporation. The residue was chromatographed on silica gel, eluting with methylene chloride/ethyl acetate (30:1), to afford the pure product 57 (4.6 g, 87%) as an oil. 1H NMR (300 MHz, CDCl3) δ 1.44 (s, 9H), 1.51 (m, 2H), 1.65 (m, 2H), 2.69 (t, 2H), 3.14 (m, 2H), 4.52 (br s, 1H), 7.27 (d, 2H), 7.56 (d, 2H).

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