[CH2:1]([O:3][C:4]([C:6]1[S:7][C:8](Br)=[CH:9][CH:10]=1)=[O:5])[CH3:2].C(N(CC)CC)C.[CH3:19][C:20]([CH3:24])([CH3:23])[C:21]#[CH:22]>CN(C=O)C.[Cu](I)I.C1C=CC(/C=C/C(/C=C/C2C=CC=CC=2)=O)=CC=1.C1C=CC(/C=C/C(/C=C/C2C=CC=CC=2)=O)=CC=1.C1C=CC(/C=C/C(/C=C/C2C=CC=CC=2)=O)=CC=1.[Pd].[Pd]>[CH2:1]([O:3][C:4]([C:6]1[S:7][C:8]([C:22]#[C:21][C:20]([CH3:24])([CH3:23])[CH3:19])=[CH:9][CH:10]=1)=[O:5])[CH3:2]A mixture of 5-Bromo-thiophene-2-carboxylic acid ethyl ester (7 g, 30 mmol), copper iodide (1.2 g, 6 mmol), triethylamine (20 mL) in DMF (100 mL) was degassed in a 350 mL pressure bottle. Then tris(dibenzylideneacetone)dipalladium(0) (2.1 g, 3 mmol) and 3,3-dimethyl-but-1-yne (18.3 mL, 150 mmol) were added and heated at 80 degree for 3 hours. The reaction mixture was filtered on celite and washed with ethyl acetate. The solution was diluted with water and extracted twice with ethyl acetate. The organic phases were combined and washed with water. After drying and concentration, the crude residue was purified by flash chromatography to yield 6.9 g (95%) of 5-(3,3-Dimethyl-but-1-ynyl)-thiophene-2-carboxylic acid ethyl ester as a yellow oil.
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