2-Methyl-2-butene → 5-(4-Chlorophenylthio)thiophene-2-carboxylic acid

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Reaction Steps

The product of Step 14a (6.1 g, 24 mmol) is dissolved in a mixture of THF, t-BuOH, and water (3:3:1, 255 mL). 2-Methyl-2-butene (20.3 mL, 192 mmol) is added followed by KH2PO4 (9.8 g, 72 mmol) and then NaClO2 (80%, 8.17 g, 72.3 mmol). The mixture is stirred at rt for 2 hr. Aqueous KHSO4 (0.5M, 200 mL) is added and the organic solvents are removed in vacuo to produce an aqueous suspension of the product. The precipitate is collected by filtration, dissolved in 1N NaOH and washed two times with ether. The aqueous solution is then acidified to pH<6 with concentrated HCl and a precipitate formed. The precipitate is collected by filtration and washed with 0.5M KHSO4 then water. The solid is dried in vacuo to give 5-(4-chlorophenylsulfanyl)-thiophene-2-carboxylic acid (5.7 g, 87%). MS for C11H7ClO2S2 (ESI) (M−H)− m/z 269.

Provenance & Evidence