N#N.[CH3:3][C:4]1([C:9]2[S:10][CH:11]=[CH:12][CH:13]=2)[O:8][CH2:7][CH2:6][O:5]1.CN(C)CCN(C)C.[Li]CCCC.CN([CH:30]=[O:31])C>C1COCC1.CCCCCC>[CH3:3][C:4]1([C:9]2[S:10][C:11]([CH:30]=[O:31])=[CH:12][CH:13]=2)[O:5][CH2:6][CH2:7][O:8]1In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), to a solution of commercially available 2-methyl-2-thiophen-2-yl-[1,3]dioxolane (5.00 g, 28.49 mmol) in THF (145.0 mL) at −78° C. was added dropwise N,N,N′,N′-tetramethyl-ethylendiamine (4.41 mL, 29.06 mmol) followed by n-BuLi (18.14 mL of a 1.6M solution in hexane, 29.06 mmol), maintaining the temperature at −78° C. The reaction mixture was then stirred for 2 h at −78° C. before DMF (6.74 mL, 87.22 mmol) was added dropwise. The cooling bath was removed and the reaction mixture was stirred for 16 h. The reaction mixture was poured in sat. aq. NaH4Cl (200 mL) and extracted with EA (2×200 mL). The combined org. extracts were dried over MgSO4, filtered, and the solvent was removed under reduced pressure to give crude 5-(2-methyl-[1,3]dioxolan-2-yl)-thiophene-2-carbaldehyde as an yellow oil. LC-MS-conditions 02: tR=0.87 min; [M+AcCN+H]+=240.32. The crude material was dissolved, under inert atmosphere (N2) in MeOH (51.2 mL) and treated at 0° C., portionwise, over 20 min, with NaBH4 (1.35 g, 34.19 mmol in five equal portions). The reaction mixture was stirred at rt for 45 min. The reaction mixture was poured in water (90 mL) and the aq. layer was extracted with EA (2×225 mL). The combined org. extracts were dried over MgSO4, filtered, and the solvents were removed under reduced pressure. Purification of the residue by FC (50:50 hept-EA) gave the title compound. TLC: rf (50:50 hept-EA)=0.40. LC-MS-conditions 02: tR=0.72 min; [M+H]+=201.46.
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