Hydrochloric Acid → Indole

Participants

Reaction Conditions

Reaction Steps

In a 5-L cylindrical reactor, 3 N HCl (750 mL) was added to the eutomer cinchonidine salt (256 g, 0.485 mol) in isopropyl acetate (1.5 L) at 20-25° C. The mixture was stirred for 10-15 min then separated into two layers. The isopropyl acetate layer was set aside. The lower aqueous layer was extracted with isopropyl acetate (250 mL). The combined isopropyl acetate layers were with H2O (750 mL). Heptane (1.75 L) was added to the isopropyl acetate layer then the isopropyl acetate and heptane solution (3.7 L) was distilled under atmospheric pressure to ˜¼ its original volume, approximate 1.0 L. Heptane (1 L) was added over 15-20 min at 85-90° C. then the mixture cooled to 0-5° C. over 1-2 h. The mixture was stirred at 0-5° C. for 1-2 h then filtered through a Buchner funnel lined with polypropylene cloth. The solid was washed with heptane (2×150 mL) then the product dried under vacuum under a bed of N2 for 14 h to give 89.6 g (29.9% overall yield from racemic acid) of the eutomer indole acid as an off-white solid.

Provenance & Evidence