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Sodium hydride (60% dispersion in oil, Alfa) was rendered oil-free by thoroughly and rapidly washing with pentane and then vacuum-drying. Oil-free sodium hydride (4.40 g, 0.110 mole, 1.1 eq) was added in about 20 portions over 25 min to a solution of 5-chloropentyne (10.6 mL, 0.100 mole, 1.0 eq), trifluoroacetamide (14.13 g, 0.125 mole, 1.25 eq), and sodium iodide (14.99 g, 0.100 mole, 1.0 eq) in dry dimethylformamide (250 mL, Aldrich). The reaction mixture was stirred at 25° for 4.5 h and at 60° for 21 h. After cooling, the reaction mixture was added to a solution of potassium dihydrogen phosphate (43.5 g, 0.250 mole, 2.0 eq) in water (500 mL). This solution was extracted with pentane (2×500 mL) and ether (3×500 mL). The combined organic layers were washed with water (1×100 mL), dried over magnesium sulfate, and concentrated with a rotary evaporator. Fractional distillation twice through a 20 cm Vigreux column afforded 8.09 g (45%) of 5-trifluoroacetamido-1-pentyne (58) as a colorless, mobile liquid (bp 68-69° at 13 torr.)

1. washrapidly washing with pentane
2. customvacuum-drying
3. temperatureAfter cooling
4. extractionThis solution was extracted with pentane (2×500 mL) and ether (3×500 mL)
5. washThe combined organic layers were washed with water (1×100 mL)
6. dry with materialdried over magnesium sulfate
7. concentrationconcentrated with a rotary evaporator
8. distillationFractional distillation twice through a 20 cm Vigreux column