Lithium Hydroxide → Thieno[2,3-d]thiophene-2,6-dicarboxylic acid

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Reaction Steps

Ester deprotection (Step C) The 2,6-dicarboethoxy-3,7-diheptadecylthieno[3,2-b]thieno[2′,3′:4,5]thieno[2,3-d]thiophene (26.0 g, 30 mmol) product of Example 2, LiOH (2.9 g, 121 mmol in 29 mL water), THF (100 mL), MeOH (20 mL) and a catalytic amount (about 35 mg) of tetrabutylammonium bromide were combined in a round bottomed flask fitted with a condenser and heated at reflux overnight. Approximately 90% of the solvent was evaporated and the residue was acidified to pH 1 with concentrated hydrochloric acid to form a solid which was collected by filtration, washed thoroughly with water and methanol, and dried under vacuum to yield 3,7-diheptadecanyl thieno[3,2-b]thieno[2′:3′:4,5]thieno[2,3-d]thiophene-2,6-dicarboxylic acid (23.5 g, 96% yield). 1H NMR (D8-THF) δ 0.88 (6H, m), 1.20-1.50 (72H, m), 1.70-1.87 (4H, m), and 3.23 (4H, m).

Provenance & Evidence