Scheme 4.

Structure–reactivity relationship of catalysts and amination reagents. ^a Molecular sieves were used to remove deleterious moisture. ^b Reactions were carried out under N₂ in 1 h and then quenched with saturated aqueous NaHCO₃ solution, unless stated otherwise. The crude mixture was first subjected to acidic conditions with TsOH (1.0 equiv) and then to basic conditions with LiOH (2.5 equiv) to afford 5. ^c Conversion was measured by GC. ^d Isolated yield. ^e An oxazolidinone was isolated directly without the additional step.