Pyridine → Oxaprozin

Participants

Reaction Conditions

Reaction Steps

A clean dry reactor of 20 gallon (91 liters) capacity was charged with pyridine (9.25 kg), benzoin (16.5 kg.) and succinic anhydride (11.7 kg.). The reactor was purged with nitrogen and a nitrogen atmosphere was maintain throughout the process. The mixture was heated without agitation until it became liquid at 85° C. Agitation was commenced and the mixture was heated at 90°-95° C. for 1.5 hours. A solution of ammonium acetate (12.0 kg.) in glacial acetic acid (35.0 kg.) was charged to the header of the reactor and added to the reaction mixture over 15 minutes, maintaining the temperature between 90° and 95° C. The container for the solution and the header were washed with glacial acetic acid (4.0 kg.) and the washing liquid was added to the reaction mixture. The reaction mixture was held at 90°-95° C. for 2 hours. The reaction mixture was cooled to 50° C. and transferred via a line filter to a reactor of 50 gallon (227 liters) capacity. The first reactor, lines and filter were washed with glacial acetic acid (4.0 kg.) which was combined with the reaction mixture. The reaction mixture was heated with agitation to 90°-95° C. over 30 minutes and water (21.0 kg.) was added maintaining the temperature at 90°-95° C. The reaction mixture was then cooled to 20°-25° C. over 55 minutes by means of water in the jacket of the reactor and then cooled to 10°-15° by means of brine in the jacket and left overnight. The product was filtered on a ceramic filter and sucked well dry. The product on the filter was washed with a pre-filtered mixture of glacial acetic acid (25.5 kg.) and water (12.5 kg.) and sucked well dry. Pre-filtered water (50.0 kg.) and the filter cake were added to a reactor of 50 gallon (227 liters) capacity. The mixture was stirred at room temperature for 30 minutes and filtered on a ceramic filter and the product was sucked well dry. The product on the filter was washed twice with pre-filtered water (10 kg. each time) and sucked well dry. The product was then dried in a Mitchell oven at 80° C. for 16-18 hours. The yield of crude β-(4,5-diphenyloxazol-2-yl)propionic acid was 15.9 kg. (69.8%). This material only just failed specification for acceptable purity because although TLC analysis showed only very faint trace impurities, their number was considered excessive.

Provenance & Evidence