[CH3:1][C:2]([O:6][Si:7]([CH3:10])([CH3:9])[CH3:8])([CH3:5])[C:3]#[CH:4].C([Li])CCC.CN([CH:19]=[O:20])C.OP([O-])(O)=O.[K+]>C1COCC1.C1CCCCC1.CCOCC>[CH3:1][C:2]([O:6][Si:7]([CH3:10])([CH3:9])[CH3:8])([CH3:5])[C:3]#[C:4][CH:19]=[O:20]
Dissolve 3-methyl-3-trimethylsilyloxy-1-butyne (8.35 g, 53.4 mmol) in THF (200 mL) and cool to 40° C. Add n-butyllithium (26.7 mL of a 2.0 M solution in cyclohexane, 53.4 mmol, 1 eq.) dropwise over a 5 minute period. Stir for 10 min., then add dry DMF (8.27 mL, 7.81 g, 107 mmol, 2 eq.) in one portion. After 30 min., pour into a cooled (0° C.), vigorously stirred mixture of 10% KH2PO4 (290 mL, 213 mmol) and ether (300 mL). Separate the layers and wash the organic layer with water (2×200 mL). Dry (MgSO4), filter, and concentrate to give 9.4 g (94% crude) of a light oil. Use without further purification. TLC: Rf=0.40 (20:1 hexanes/EtOAc); 1H NMR (CDCl3, 300 MHz) δ 9.03 (s, 1H), 1.35 (s, 6H), 0.02 (s, 9H).
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