A two-step synthesis of aminopropylpiperidines via aminopropargylpyridines, suitable for the synthesis of a new class of 5-HT4 ligands

A rapid and flexible synthetic approach to {[bis(tert-butoxycarbonyl)amino]propyl}piperidines 5 and related compounds is described. The key step is a three-component coupling process of 2-, 3- or 4-bromopyridine, propargyl bromide and potassium di-tert-butyliminodicarbonate under palladium-copper catalysis leading to 2-, 3- or 4-{[bis(tert-butoxycarbonyl)amino]-propargyl}pyridines 4 followed by a catalytic reduction step.