5-Substituted-3-(substituted)phenyl-1,3,4-oxadiazolin-2(3H)-ones. Synthesis and reactions with nucleophilic reagents

A new synthesis of 4,4-dialkyl-2-(substituted)phenylsemicarbazides has been developed. The procedure begins with a 5-substituted-3-(substituted)phenyl-1,3,4-oxadiazolin-2(3H)-one, 3 , which is treated with dialkylamine to give a 1-acyl-4,4-dialkyl-2-(substituted)phenylsemicarbazide, 7 . Subsequent base-catalyzed hydrolysis of 7 gives 4,4-dialkyl-2-(substituted)phenylsemicarbazides, 14 , in high yield. With a variety of nucleophilic reagents, the compounds 3 also undergo ring opening.