3-Bromothiophene → Di(3-thienyl)methanol

Participants

Reaction Steps

To cooled (-78° C.) solution of 3-bromothiophene (16.3 g, 0.1 mol) in THF (100 mL) was added under nitrogen, n-butyllithium (2.5M, 40 mL) and to the above mixture was added N-methyl-N-methoxyurethane (6.28 g, 0.047 mol) in 5 mL of THF over a 0.5 h period and the mixture was allowed to warm to room temperature. The mixture was quenched with saturated ammonium chloride solution and the aqueous layer was extracted with ether. The combined organic layer was dried over magnesium sulfate, concentrated in vacuo, and the oil residue was crystallized from methanol to afford 1.465 g (16%) of 1,1-di-(3-thienyl)ketone, m.p. 78°-80° C. Alternatively, 1,1-di-(3-thienyl)ketene was prepared as follows: To 100 mL of THF cooled to -78° C. under nitrogen was added 2.5M n-butyllithium (36 mL), and 14.67 g (0.09 mol) of 3-bromothiophene was added and the resulting mixture was stirred for 30 min. To the above mixture was added 3-thiophenecarboxaldehyde (10 g, 0.089 mol) in 10 mL of THF and the mixture was stirred, allowing it to reach room temperature. Saturated ammonium chloride solution was added to the reaction mixture, the aqueous layer was extracted with ether, and the combined organic layer was concentrated in vacuo to yield 17.26 g (98.9%) of 1,1-di(3-thienyl)methanol, as an oil. Chromium trioxide (1.4 g) was dissolved in 12 mL of water and 24 mL of acetic acid, and the resulting mixture was added dropwise to 1,1-di(3-thienyl)-methanol in 30 mL of acetic acid over a 1 h period. The above mixture was stirred for 1 h with cooling (20° C.) in an ice-water bath. The mixture was diluted with 150 mL of water, extracted with methylene chloride, and the organic layer was washed with saturated sodium bicarbonate solution, dried over sodium sulfate, and concentrated in vacuo to yield an oil, which was crystallized in methanol to afford 1.85 g (47.7%) of 1.1-di(3-thienyl)ketone, as a solid, m.p. 79°14 81° C.

Provenance & Evidence