Water → 5-Bromothiophene-2,3-dicarboxylic acid

Participants

Reaction Conditions

Reaction Steps

A suspension of 5-bromo-3-methyl-thiophene-2-carboxylic acid (177 g, 0.80 mol), example 1-b, and sodium hydroxide (720 g, 18 mol) in 3 L of water was heated to 80° C. Potassium permanganate (513 g, 3.25 mol) was added in 25 g portions to the warm solution over 2-3 hours. The resultant suspension was heated to reflux temperature for 2 hours and then cooled to room temperature. The solid was filtered off and washed twice with 1 N NaOH and twice with water. The aqueous solution was acidified to pH <3 with concentrated sulfuric acid. The resulting white precipitate was collected on a medium fritted glass filter, washed twice with cold water, and dried under high vacuum to produce 112 g of a white solid. MS: (−) m/z 248.91, 250.98 (M−1, 79Br/81Br)

Provenance & Evidence