Acetic Acid → N,N'-Dicyclohexylurea

Participants

Reaction Steps

A solution of (3R,6R,7R)-3-hydroxy-7-phenylacetamido cepham (6.0 g., 20.5 mmole) and dicyclohexylcarbodiimide (11.65 g., 56.6 mmole) in dimethyl sulphoxide (50 ml.) was treated with pyridine trifluoroacetate (1.37 g., 7.1 mmole) and the mixture was stirred at 26° for 11/2 hours. Acetic acid (6 ml.) and water (2 ml.) were added and the mixture was stirred for 30 minutes before being diluted with ethyl acetate (250 ml.) and filtered to give dicylohexylurea (10.04 g., 79%) as colourless prisms. The filtrate was washed with saturated aqueous sodium hydrogen carbonate (2 × 200 ml.), dried, and evaporated under reduced pressure to give a brown solid (7.65 g.). The solid was refluxed with acetonitrile (100 ml.) for 5 minutes, filtered to give more dicyclohexyl urea (0.4 g., 3.2%) and the filtrate was evaporated under reduced pressure. The resulting brown solid was dissolved by heating under reflux with isopropyl alcohol (150 ml.) for 15 minutes and on cooling, crystals of (6R,7R)-3-keto-7-phenylacetamidocepham (3.6 g., 60.5% in two crops) separated out; m.p. and NMR were in agreement with standards.

Provenance & Evidence