Ethylene Glycol → 2-(3-Bromothiophen-2-yl)-1,3-dioxolane

Participants

Reaction Steps

Pyridinium tosylate (1 g., 4 mmoles) was added to a mixture of 3-bromothiophene-2-carboxaldehyde (2) (18.7 g., 97.9 mmole), ethylene glycol (22 mL., 24.8 g., 400 mmole) and dry toluene (100 mL). The mixture was refluxed and the water removed by a Dean-Stark trap. After 1 hour, TLC (10% EtOAC/hexane) showed the reaction was complete. The mixture was cooled to room temperature and partitioned between ether (100 mL) and water (100 mL) components. The organic layer was separated and extracted with water (3×50 mL) and then with a saturated solution of sodium bicarbonate (25 mL). The resulting extract was dried (MgSO4), filtered and evaporated in vacuo to leave 21.5 g, of crude product. This product was distilled to give 17.6 g of 3 -Bromo-2-(2-dioxolanyl)thiophene (3), bp: 86°-87° C./0.5 mm.

Provenance & Evidence