反应详情

A solution of 25.01 g (136.0 mmol) of 5-trimethylsilyl-2-furancarboxylic acid (Carpenter, A. J. and Chadwick, D. J., Tetrahedron Lett., 26, 1777 (1985)) in 50 mL of dry tetrahydrofuran is added over 10 minutes to a -76° C. solution of freshly generated lithium diisopropylamide (328.0 mmol, 2.41 equiv) in dry tetrahydrofuran (175 mL) under nitrogen atmosphere and the resulting mixture is stirred at -76° to 65° C. for 1.5 hours. The reaction is recooled to -76° C. and treated with 23.58 g (151.0 mmol, 1.11 equiv) of diisopropyl sulfide in 25 mL of tetrahydrofuran and the resulting mixture is stirred for 4 hours while slowly warming to room temperature. The reaction is poured onto 1.5 L of water and the aqueous mixture is extracted with diethyl ether (200 mL, 3x), treated with 400 g of ice, and acidified with concentrated hydrochloric acid. The resulting precipitate is collected by vacuum filtration and recrystallized from diethyl ether/cyclohexane to give 18.22 g (35.14 g theo., 52%) of analytically pure 3-isopropylthio-5-trimethylsilyl-2-furancarboxylic acid as a tan solid; mp 181°-183° C.

1. customis recooled to -76° C.
2. stirringthe resulting mixture is stirred for 4 hours
3. extractionthe aqueous mixture is extracted with diethyl ether (200 mL, 3x)
4. additiontreated with 400 g of ice
5. filtrationThe resulting precipitate is collected by vacuum filtration
6. customrecrystallized from diethyl ether/cyclohexane