[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([S:8](/[N:11]=[CH:12]/[C:13]2[CH:14]=[N:15][CH:16]=[N:17][CH:18]=2)(=[O:10])=[O:9])=[CH:4][CH:3]=1.C[Si](C)(C)[C:21]([CH:23]=[CH2:24])=[CH2:22].C1C[O:30]CC1>>[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([S:8]([N:11]2[CH2:24][CH2:23][C:21](=[O:30])[CH2:22][CH:12]2[C:13]2[CH:18]=[N:17][CH:16]=[N:15][CH:14]=2)(=[O:9])=[O:10])=[CH:4][CH:3]=1To a solution of 69 (2.12 g, 7.5 mmol) in THF (15 mL) was added 2-(trimethylsilyl)-1,3-butadiene (70, 2.18 g, 15 mmol). The reaction was heated at reflux for 36 hours. The reaction mixture was cooled to room temperature and concentrated in vacuo to yield 3.33 g crude material. The residue was purified by flash chromatography (3:1 hexanes/EtOAc) to yield 1.05 g (40%) 71 as a yellow solid. 1H NMR (CDCl3) δ 9.16 (s, 1H), 8.63 (s, 2H), 7.85 (d, 2H), 7.55 (d, 2H), 5.65 (d, 1H), 4.11-4.04 (m, 1H), 3.24-3.14 (m, 1H), 2.96-2.82 (m, 2H), 2.55-2.49 (m, 1H), 2.40-2.34 (m, 1H).
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