Carbon Dioxide → 2-Methyl-3-pyrrol-1-yl-benzoic acid

Participants

Reaction Steps

A sample of 1.27 grams (0.052 mole) of magnesium metal was placed in a Morton Flask. The flask and contents were flame-dried under a nitrogen atmosphere. After the flask and contents were cooled, 10.0 grams (0.052 mole) of 1-(3-chloro-2-methylphenyl)pyrrole, a few crystals of iodine, and 20 ml of tetrahydrofuran were added; followed by three drops of methyl iodide. The reaction was commenced by the addition of an external Grignard Reagent of magnesium, methyl iodide and tetrahydrofuran. Once started, the reaction warmed the stirred reaction mixture to reflux. A precipitate appeared and was dissipated by the addition of 20 ml of tetrahydrofuran. The reaction mixture was heated under reflux for 22.5 hours. After this time the reaction mixture was cooled and crushed dry ice (CO2) was added until a thick slurry formed. An additional 20 ml of tetrahydrofuran was added and the thick slurry was reformed by the addition of more dry ice. The reaction mixture was stirred while being allowed to warm to ambient temperature. After the reaction mixture had warmed an aqueous solution saturated with ammonium chloride was added until a solid precipitate appeared. Upon complete addition the reaction mixture was stirred for 2.5 hours then 150 ml of diethyl ether was added. The mixture was filtered through a small amount of magnesium sulfate. The filtrate was concentrated under reduced pressure to a residual oil. The residual oil was dissolved in diethyl ether and extracted with three portions of 200 ml each of aqueous 2 N sodium hydroxide. The combined basic layers were washed with 200 ml of diethyl ether and acidified to pH=1 with concentrated hydrochloric acid. A solid precipitate formed. The mixture was cooled and extracted with four portions of 200 ml each of diethyl ether. The combined extracts were dried with magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure to give 9.8 grams of 2-methyl-3-(pyrrol-1-yl)benzoic acid; mp 146°-148.5° C.

Provenance & Evidence