5-Bromofurane-2-sulfinic Acid Lithium Salt

2,5-dibromofurane 1.570g (TCI-US, 6.95 mmol) solution in anh THF 15mL was cooled under Ar to -78C and BuLi 2.5M solution in hexanes 2.6mL (6.50 mmol) was added dropwise over 8 min period. The mixture was stirred for additional 15 min, then quenched at -78C with a stream of sulfur dioxide gas (Aldrich lecture bottle; above the reaction mixture level) for about 10 min; the volume of reaction mix increased by about 8 mL. The cooling bath was removed and the excess of condensed SO2 was blown off with a stream of Ar gas (about 30 min at RT). The reaction mixture was portioned between water 100mL and hexanes 100mL, the organic phase was re-extracted with additional water (2x25mL). The aqueous extracts were washed with additional hexanes (40mL). The aqueous extracts were combined and evaporated. The obtained solid residue was dried on highvac. Y=1.274g (90% th) of a light tan semicrystalline solid, approx 95% pure by NMR, HPLC.

1H(d6-DMSO, 400MHz): 6.430(d, 3.2Hz, 1H), 6.276(d, 3.2Hz, 1H); 13C(d6-DMSO, 100MHz): 172.38, 119.89, 111.68, 107.79; LC/MS(-ESI): 209, 211