Synthesis of diethyl 3,3 -([1,1 -biphenyl]-4,4 -diylbis(azanediyl))bis(5-oxo-2,5-dihydroisoxazole-4-carboxylate)

The synthesis of ethyl 3-phenylamino-5-oxo-2,5-dihydroisoxazole-4-carboxylate (1) has been reported by Worrall [1,2]. Reaction of 4,4 -diaminobiphenyl with thiophosgene at room temperature afforded the corresponding diisothiocyanate (2) [3]. Reaction of the sodium salt of diethyl malonate in EtOH with 4,4 -diisothiocyanato-1,1 -biphenyl (2) gave the tetra ethyl 2,2 -(([1,1 -biphenyl]-4,4 -diylbis(azanediyl))bis(carbonyl))dimalonate (3) in good yield, which was converted to the diethyl 3,3 -([1,1 -biphenyl]-4,4 -diylbis(azanediyl))bis(5-oxo-2,5-dihydroisoxazole-4-carboxylate) (4) by reaction with two equivalents of hydroxylamine under reflux conditions.