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.