Cyclization of N-formyl-alpha,alpha-dimethyl-b-phenethylamine (I) with phosphorous pentoxide in refluxing toluene led to isoquinoline (II), which was oxidized with 3-chloroperbenzoic acid (III) in dichloromethane at 0 C to give oxaziridine (IV). Finally, oxazirine (IV) was rearranged with sulfuric acid in aqueous methanol at room temperature to afford the target N-oxide.