Efficient Synthesis of N-Alkyl Tetrahydroisoquinolines by Reductive Amination

An expedient access to diverse N-alkyl 1,2,3,4-tetrahydroisoquinolines is reported by reductive amination of aldehydes and ketones with tetrahydroisoquinoline (THIQ) in the presence of Ti(Oi-Pr) 4 and NaBH 4 . The N-alkyl THIQ products were rapidly purified by flow-through catch and release technique using commercially available polymer-supported sulfonic acid, MP-TsOH columns.