Org Prep Daily

June 25, 2007

5-Bromofurane-2-sulfinic Acid Lithium Salt

Filed under: procedures — milkshake @ 10:55 pm

sulfinic.gif

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

5 Comments »

  1. do butyl lithium reactions have to be under argon?

    im trying to lithiate 2 bromo pyridine. Then after 3hrs of reacting at -78 degrees under nitrogen in THF, I add a brominated huge alkyl group to try and have a halogen lithium exchange but it does not seem to work.

    any tips would be greatly appreciated.

    Comment by dro — August 9, 2007 @ 11:29 am

  2. I dont know what are you trying to do: is is 2-pyridinyl alkane? You neeed to be more specific.

    Also, 2-pyridyl lithiums are quite unstable and aryl lithium do not couple with alkyl bromides directly, they need a Fe salt as a catalyst. Try to look up Furstner, he did a work in the area. Alternatively you can use CuI or CuCN as a catalyst.

    Comment by milkshake — August 10, 2007 @ 4:02 am

  3. What would happen if you substituted SOCl2 for SO2?

    Comment by Zeph — August 18, 2007 @ 10:02 am

  4. That’s a good point – I don’t know. Probably you would end up with lots of diaryl sulfoxide.

    Comment by milkshake — August 19, 2007 @ 12:49 pm

  5. I’m betting that it would give the chloride, as in -SO2Cl. Subsequent distillation would give the product?

    Comment by Zeph — August 20, 2007 @ 6:27 am


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