Benzonitrile → Ethyl 5-phenyl-1,2,4-thiadiazole-3-carboxylate

Participants

Reaction Steps

A solution of 8.76 g (0.050 mol) of ethyl 2-oxo-1,3,4-oxathiazole-5-carboxylate in 180 g (35 equiv., 1.75 mol) of redistilled benzonitrile was held at reflux for 72 hours. The solution, which contained the product in 62% yield (gc assay), was concentrated under vacuum to 90° C (0.5 torr). The residue was heated with 200 ml of hexane at reflux; the supernatant was decanted, treated with charcoal, filtered, and concentrated under vacuum to 6.1 g of oil and solid. The mixture was chromatographed on 200 g of silica gel (Woelm, for dry column chromatography) with benzene. The first 500 ml of eluate contained 0.8 g of product and impurities. The next 1200 ml of eluate gave 3.82 g (33%) of pure liquid product (gc assay), which crystallized after several months, mp 32°-35° C; nD25 = 1.5937; mass spectrum m/e (rel. intensity, fragment) 234 (18, M+ ), 206 (3, M+ -C2H4), 189 (10, M+ -OEt), 135 (100, M+ -EtO2CCN), 103 (14, C6H5CN+).

Provenance & Evidence