Phenyl isocyanate → (trans)-N-(7,8-Dihydro-7-hydroxy-6,6-dimethyl-6H-[1]benzopyrano[6,7-c][1,2,5]oxadiazol-8-yl)-N'-phenylurea

Participants

Reaction Steps

To a solution of 7,8-dihydro-6,6-dimethyl-7-hydroxy-8-amino-6H-pyrano[2,3-f]benzo-2,1,3-oxadiazole (0.25 g, 1.06 mmoles) (prepared as described in part I of Example 1) in ethanol (2.5 ml) at 60° C. was added phenyl isocyanate (0.126 g, 1.06 mmoles). The reaction was heated at reflux for three hours, cooled to room temperature and diluted with isopropyl ether (5 ml). The product slowly crystallized from solution. It was collected via suction filtration and dried under vacuum to obtain 0.18 g of the desired compound as a beige solid. The residue obtained upon evaporation of the mother liquor was chromatographed on silica gel eluting with 1:1 ethyl acetate/hexane to afford an additional 0.16 g of product. The two crops were combined and triturated with isopropyl ether to obtain 0.30 g of the title compound as an off-white solid (m.p. 215°-216° C.).

Provenance & Evidence