Intramolecular N to N acyl migration in conformationally mobile 1′-acyl-1-benzyl-3′,4′-dihydro-1′H-spiro[piperidine-4, 2′-quinoline] systems promoted by debenzylation conditions (HCOONH 4/Pd/C)

Abstract

We report an efficient and useful synthesis of new attractive spiropiperdine scaffolds 4 based on an intramolecular acyl transfer process in 1'-acyl-1-benzyl-3',4'-dihydro-1'H-spiro[piperidine-4,2'-quinolines] 3 using simple and mild debenzylation reaction conditions (HCOONH4/Pd/C). The compounds 3 were prepared by acylating 1-benzyl-4'-methyl-3',4'-dihydro-1'H- spiro[piperidine- 4,2'-quinolines] 2 that are easily available from 1-benzyl-4-piperidone 1. The intramolecular character of this process was proven primarily through a crossover experiment technique. Through an examination of all spectroscopic information (1H, 13C NMR, VT -1H NMR, and 2D NMR) it was possible to correctly predict amide configurations and piperidine ring conformations of starting and final spiropiperidine compounds. © Versita Sp. z o.o.