Methane → 2,4-Dimethylthiophene-3-carbaldehyde
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Br[C:2]1[C:6]([CH3:7])=[CH:5][S:4][C:3]=1[CH3:8].[Li]CCCC.CN([CH:17]=[O:18])C.C>C(OCC)C.CCCCCC>[CH3:8][C:3]1[S:4][CH:5]=[C:6]([CH3:7])[C:2]=1[CH:17]=[O:18]Br[C:2]1[C:6]([CH3:7])=[CH:5][S:4][C:3]=1[CH3:8].[Li]CCCC.CN([CH:17]=[O:18])C.C>C(OCC)C.CCCCCC>[CH3:8][C:3]1[S:4][CH:5]=[C:6]([CH3:7])[C:2]=1[CH:17]=[O:18]A solution of 3-bromo-2,4-dimethylthiophene, B8, (5.9 g, 0.031 mol) in 200 mL of diethyl ether was cooled to -78° C., and a solution of n-BuLi (25.0 mL, 1.6M) in hexanes was added dropwise. When the addition was complete, the reaction was stirred at -78° C. for 4 h. TLC analysis indicated very little conversion so reaction mixture was warmed slowly to -25° C. Then a solution of DMF (4.5 g, 0.062 mol) in 25 mL of ether was cannulated into the reaction mixture which was allowed to warm to ambient temperature and was stirred overnight. The reaction was quenched with water and extracted twice with diethyl ether. The organic extracts were combined, washed with twice with water and then brine and dried (MgSO4). The solution was filtered and concentrated to provide an amber oil which was dissolved in hexane. The solution was treated with charcoal, filtered through Dicalite, and concentrated to give 2,4-dimethylthiophene-3-carboxaldehyde, C,8, which was used directly in the next step. ##STR60##
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