4-Bromo-3-thiophenecarboxaldehyde

A stirred and cooled solution of thiophene (185 mL, 2.3 mol) at 0 °C in chloroform was treated dropwise with bromine (500 ML, 1560 g, 9.75 mol) for 5 h. During the last hour bromine was added without cooling the reaction mixture. Then the mixture was stirred and heated at reflux for 5 h, cooled to room temperature, quenched with 3 M aqueous NAOH, and stirred vigerously to consume excess bromine. The aqueous layer was separated, the organic phase was washed with water, and then with acetone (150 mL) to remove remaining water. The organic residue was dried and then dissolved at reflux in chloroform (1 L). When cooling, the target tetrabromo- thiophene was precipitated as colorless crystals (693 g, 75percent). A solution of this tetrabromo- thiophene (47 g, 0.12 mol) in dry diethyl ether (300 ML) was cooled to 0 °C and treated dropwise with butyllithium in hexane (150 ML, 0.24 mol, 1.6 M) for 80-90 min under argon. Then the mixture was stirred for an additional 20 min, and ice water (250 mL) was added carefully with stirring. The organic phase was separated, the aqueous phase extracted twice with ether, and the organic extracts all combined, dried over anhydrous calcium chloride, and concentrated in vacuo. The residue was distilled at 15 MMHG to give 22 g (77percent) of 3, 4-dibromothiophene. A solution of this 3, 4-dibromothiophene (72 g, 33 mL, 0.3 mol) in dry ether (120 mL) was cooled TO-78 °C, added to a solution of nBuLi (206 mL, 0.33 mol, 1.6 M) AT-78 °C, and stirred for 5 min. A cold - 78 °C solution OF DMF (35 mL, 33 g, 0.45 mol) in dry ether (120 mL) was slowly added to the reaction mixture AT-78 °C. After 10 min, the cold bath was removed and an aqueous HCI (150 mL, 6N) solution was added carefully, the mixture warmed to 23 °C and the aqueous phase separated and washed further with ether. The organic extracts were then combined, washed with saturated aqueous sodium bicarbonate, and the organic partition evaporated. The residue was distilled twice under vacuum to provide pure title compound (40 g, 69percent)

4-Bromo-3-thiophenecarbaldehyde is used in the dehalogenation and hydrogenation of halogenated heteroatom aldehydes. Also used in the production of NIR-absorbing polycarboxylic acids as polymer dye for dye sensitized solar cells.

Molecular Weight:191.05
XLogP3:1.8
Hydrogen Bond Acceptor Count:2
Rotatable Bond Count:1
Exact Mass:189.90880
Monoisotopic Mass:189.90880
Topological Polar Surface Area:45.3
Heavy Atom Count:8
Complexity:96.4
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes