[CH3:1]C([O-])(C)C.[K+].[F:7][C:8]1[CH:17]=[CH:16][C:15]2[N:14]=[CH:13][C:12]([O:18][CH3:19])=[N:11][C:10]=2[C:9]=1[CH:20]=O.[NH4+].[Cl-].O>[Br-].C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.C1COCC1>[F:7][C:8]1[C:9]([CH:20]=[CH2:1])=[C:10]2[C:15]([N:14]=[CH:13][C:12]([O:18][CH3:19])=[N:11]2)=[CH:16][CH:17]=1
Methyl triphenyl phosphonium bromide (154 g, 430 mmol) was suspended in THF (1 L) and cooled to 0° C. KOtBu (44.4 g, 400 mmol) was added in one portion and the yellow suspension was stirred at 0° C. for 15 min before a solution of 6-fluoro-3-methoxyquinoxaline-5-carbaldehyde (71 g, 340 mmol) in THF (550 mL) was added dropwise over 70 min. The mixture was stirred at 0° C. for 60 min. Sat. NH4Cl solution (250 mL) and water (250 mL) were added and the phases were separated. The org. layer was dried over MgSO4, filtered and concentrated to dryness. The residue was purified by two filtrations over a plug of silica gel (2×250 g) using an Hept/EA (2:1) mixture as eluent to afford the title alkene as an orange solid (62.7 g, 89% yield).
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