Br[C:2]1[CH:3]=[CH:4][C:5]2[O:9][CH2:8][C:7]([CH3:11])([CH3:10])[C:6]=2[CH:12]=1.[Li]CCCC.CN([CH:21]=[O:22])C.O>C1COCC1>[CH3:10][C:7]1([CH3:11])[C:6]2[CH:12]=[C:2]([CH:21]=[O:22])[CH:3]=[CH:4][C:5]=2[O:9][CH2:8]1
To a solution of 5-bromo-3,3-dimethyl-2,3-dihydro-benzofuran (example 1f) (15.90 g, 70.01 mmol) in dry THF (100 mL) at −78° C., under argon, was added dropwise n-BuLi (1.6 M in hexane, 105 mmol, 42 mL). The mixture was stirred for 5 minutes then DMF (16.3 mL, 210 mmol) was added and the mixture was quickly warmed up to −50° C. and then to 0° C. for 3 hrs. Water was added slowly and the solution extracted with ethyl acetate. The organic layer was further washed with water, brine, dried (MgSO4), filtered and evaporated to give 13.15 g of 3,3-dimethyl-2,3-dihydro-benzofuran-5-carbaldehyde use as this in the next step. 1H NMR (300 MHz; CDCl3): 1.38 (s, 6H), 4.36 (s, 2H), 6.89 (d, J=7.8 Hz, 1H), 7.68 (m, 2H), 9.85 (s, 1H).
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