Triethylamine → (4-Chlorophenyl)isopropylketene

Participants

Reaction Conditions

Reaction Steps

A sample of 53.2 g of isopropyl(4-chlorophenyl)acetic acid was treated with 21.5 ml of thionyl chloride in a 500 ml flask and heated slowly to 80° C. and maintained at 80° C. for 20 minutes. The reaction mixture was allowed to stand at room temperature for 2 days. The volatiles were stripped to 75° C. at 0.5 mm Hg. The resulting yellow liquid was diluted with 250 ml of methylene chloride followed by addition of 38.0 g of triethylamine. The mixture was stirred until triethylamine hydrochloride began to precipitate after 30 minutes. After 16 hours, the reaction mixture was filtered and solid triethylamine hydrochloride was washed with heptane. Most of the solvent was stripped from the filtrate by rotary evaporation at 50° C. The residue was diluted with 75 ml of heptane and additional triethylamine hydrochloride was removed by filtration as above. The filtrate was restripped and rediluted with 75 ml heptane and refiltered with the aid of 25 ml of heptane. The filtrate was cooled in dry ice, seeded and crystallized. The resulting crystals were filtered with a filter stick and washed with chilled heptane. The filtered solids were melted, diluted with one-half volume heptane, crystallized at -80° C. and the collected solid was melted and stored at -80° C. The filtrate solution was warmed, stripped of most solvent, then distilled through a Bantam ware short path head at 0.05 to 0.06 mm Hg from an oil bath at 90°-120° C. Total distillate was 14.5 g collected as a bright yellow-orange liquid at a head temperature of 60°-85° C. The distillate was crystallized from an equal volume of pentane at -80° C., filtered and washed twice with heptane as above to give, on warming, a second melt. The stripped filtrates totalling 5.79 g were crystallized as above in a 6-inch test tube and the melt was recrystallized immediately as described above to give a third melt. The three melts were combined and stripped to 50° C. at 5 mm Hg to give 29.4 g of the desired ketene as a yellow liquid.

Provenance & Evidence