Tetrahydrofuran → 5-Butylthiopyrrole-3-carboxylic acid
Reaction equation
[NH:1]1[CH:5]=[CH:4][C:3]([C:6]([OH:8])=O)=[CH:2]1.C([S:13]Cl)CCC.O1[CH2:19][CH2:18][CH2:17][CH2:16]1>>[CH2:16]([C:5]1[NH:1][CH:2]=[C:3]([C:6]([OH:8])=[S:13])[CH:4]=1)[CH2:17][CH2:18][CH3:19]Participants
4
Procedure
Under nitrogen, pyrrole 3-carboxylic acid (4.44 g., 40 mmoles) was dissolved in 50 ml. of tetrahydrofuran and the solution cooled in an ice-water bath. A solution of butylsulfenyl chloride (Example 46, estimated to contain 4.96 g., 40 mmoles) was added dropwise. The bath was removed and stirring continued for 1 hour at room temperature. An equal volume of ether was added, the mixture was filtered, and the filtrate evaporated to an oil (8.3 g.). The oil was chromatographed on 250 g. silica gel, with 100 ml. fractions of the ethyl acetate-1/toluene-5/5% acetic acid eluant collected. Fraction 9 was evaporated and triturated with carbon tetrachloride to yield crystalline 5-butylthiopyrrole-3-carboxylic acid (185 mg., m/e 199). Fractions 7-8 and 9-10 were combined, evaporated to gums, and rechromatographed in smaller columns, collecting 8 ml. fractions of the ethyl acerate-1/heptane-2 eluant. An additional 114 mg. of 5-butylthiopyrrole-3-carboxylic acid resulted.