[CH3:1][Si:2]([CH3:10])([CH3:9])[O:3][C:4]([CH3:8])([C:6]#[CH:7])[CH3:5].[Li]CCCC.CON(C)[C:19]([C:21]1[CH:29]=[CH:28][C:24]2=[N:25][O:26][N:27]=[C:23]2[CH:22]=1)=[O:20]>C1COCC1>[N:25]1[O:26][N:27]=[C:23]2[CH:22]=[C:21]([C:19](=[O:20])[C:7]#[C:6][C:4]([CH3:8])([O:3][Si:2]([CH3:10])([CH3:9])[CH3:1])[CH3:5])[CH:29]=[CH:28][C:24]=12To a −78° C. stirred solution of trimethyl(2-methylbut-3-yn-2-yloxy)silane (0.49 g, 2.367 mmol) in dry THF (20 mL), n-BuLi (3.70 mL, 5.917 mmol, 1.6 M in hexane) was added dropwise over 10 minutes under an inert atmosphere. The reaction mixture was stirred for 30 min at −78° C., and then a solution of N-methoxy-N-methylbenzo[c][1,2,5]oxadiazole-5-carboxamide (0.557 g, 3.550 mmol) in dry THF (10 mL) was added to reaction mixture and stirring was continued for an additional 3 h at −78° C. The reaction mixture was quenched with a saturated NH4Cl solution and extracted with EtOAc (2×20 mL). The combined organic layers were washed with water (10 mL) and brine (10 mL), dried over Na2SO4, filtered and concentrated in vacuo to obtain the crude product. The crude material was purified via silica gel column chromatography eluting with 5% EtOAc in hexanes to afford 1-(benzo[c][1,2,5]oxadiazol-5-yl)-4-methyl-4-(trimethylsilyloxy)pent-2-yn-1-one (0.45 g, 63%) as a colorless oil.
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