Dimethylformamide → 2-(5-Formylthien-2-ylethynyl)benzothiophene

Participants

Reaction Steps

A stirred solution of 10 grams (0.042 mole) of 2-(thien-2-ylethynyl)benzothiophene (prepared as in Example 2, Steps A and B) in 100 ml of tetrahydrofuran was cooled to -70° C., and 20 ml (0.050 mole) of n-butyl lithium (2.5 molar in hexane) was added portionwise, keeping the reaction mixture below -60°C. Upon completion of addition, the reaction mixture was stirred for 45 minutes as the reaction mixture temperature returned to -70°C. After this time 3.8 grams (0.052 moles) of dimethylformamide as added. Upon completion of addition, the reaction mixture was stirred at -70°C. for 5 minutes and then was allowed to warm to ambient temperature. The reaction mixture was then quenched with an aqueous solution saturated with ammonium chloride, and washed in sequence with water and then with an aqueous solution saturated with sodium chloride. The organic layer was absorbed into 15 grams of silica gel which was in turn placed on a 2.5 cm long silica gel column. Elution was accomplished with a 1:1 hexane and ethyl acetate mixture. The eluate was concentrated under reduced pressure to a brown solid residue. The dried solid residue was suspended in hexane, and the hexane was decanted from the solid. The solid was dried, yielding 2.1 grams of 2-(5-formylthien-2-ylethynyl)benzothiophene. The nmr spectrum was consistent with the proposed structure.

Provenance & Evidence