[CH3:1][C:2]1[S:3][CH:4]=[C:5]([C:7]2[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=2)[CH:6]=1.CN(CCN(C)C)C.[Li]CCCC.CN(C)[C:28](=O)[O:29]CC.[NH4+].[Cl-]>C(OCC)C.CCCCCC>[CH3:1][C:2]1[S:3][C:4]2[C:28](=[O:29])[C:12]3[CH:11]=[CH:10][CH:9]=[CH:8][C:7]=3[C:5]=2[CH:6]=1A solution of 12.88 g (0.074 mol) of 2-methyl-4-phenylthiophene, 23.4 mL (0.16 mol) of TMEDA in 200 mL of diethyl ether (ether) was treated with 100 mL (0.16 mol) of 1.6M BuLi in hexane under stirring at −40° C. Then the reaction mixture was allowed to warm up to room temperature (r.t.) and was stirred for 3 h (white precipitate forms). The reaction mixture was cooled to −40° C. and treated with 8.76 g (0.075 mol) of ethyl N,N-dimethylcarbamate in 25 mL of ether. Then the reaction mixture was allowed to warm up to r.t. and was stirred overnight. Resulting mixture was treated with 10% aqueous NH4Cl, the organic layer was separated and the organic phase was washed with 10% aqueous solution of NH4Cl and then dried by anhydrous Na2SO4. Solvent was evaporated and the residue was washed with methanol. Yield 6.8 g (46%) of red crystals.
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