合成路线1

Demethylation of methyl 4-(4-methoxyphenyl)butyrate (I) using boron tribromide affords phenol (II). Subsequent alkylation of (II) with t-butyl 2-bromoisobutyrate (III) yields ether (IV). The methyl ester group of (IV) is then selectively displaced with hydrazine hydrate to form hydrazide (V). This is condensed with p-methylbenzaldehyde (VI) to give hydrazone (VII), which is further reduced to (VIII) by catalytic hydrogenation over PtO2. Reaction of acyl hydrazide (VIII) with trimethylsilyl isocyanate leads to the acyl semicarbazide (IX). Finally, simultaneous t-butyl ester cleavage and cyclization to the target triazolone is accomplished by treatment of (IX) with several different sulfonic acids.