Versatile Synthesis of Functionalized Tetrahydroisoquinolines by Ring Transformation of 2H-Pyran-2-ones

Functionalized tetrahydroisoquinolines are convenient precursors for the construction of numerous heterocyclic compounds of therapeutic importance. In this paper we have illustrated an efficient synthesis of highly substituted tetrahydroisoquinolines from 2H-pyran-2-ones via nucleophile-mediated ring transformation with tert-butyl-4-oxopiperidine-1-carboxylate followed by acid-mediated cleavage of the tert-butyloxycarbonyl group. The products were achieved smoothly in high yields with flexibility of various substituents.