Synthesis
Example 1 Preparation of 3-iodothiophene-2-carboxylic acid
1. dissolve thiophene-2-carboxylic acid (12.8 g, 0.1 mol) in THF at -78 °C.
2. n-Butyllithium (88 mL, 2.5 M THF solution, 2.2 eq.) was added slowly dropwise and stirring was continued for 0.5 hr after completion of the drop.
3. THF solution of iodine (28 g, 1.1 eq.) was added slowly with stirring.
4. The reaction mixture was gradually warmed to room temperature and stirred at room temperature until the reaction was complete.
5. The reaction mixture was concentrated to give a crude product.
6. The crude product was dissolved in EtOAc and extracted with 10% aqueous Na2CO3 solution.
7. The aqueous phases were combined and acidified with concentrated hydrochloric acid to pH<2.
8. The acidified aqueous phase was extracted with EtOAc and the organic phases were combined.
9. The organic phase was dried over anhydrous MgSO4, filtered and concentrated in vacuo to give 3-iodothiophene-2-carboxylic acid as a yellow-orange solid (23.5 g, 95% yield).
10. The product was characterized and confirmed by HPLC and mass spectrometry.
References
[1] Patent: WO2005/12311, 2005, A1. Location in patent: Page/Page column 22
[2] Synthetic Communications, 1998, vol. 28, # 13, p. 2467 - 2481
[3] Tetrahedron, 2006, vol. 62, # 41, p. 9554 - 9570
[4] Synlett, 1998, # 1, p. 33 - 34
[5] Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1985, p. 173 - 182
