Synthesis of 4-allyl-4-arylaminopiperidines and their transformations to spiro[tetrahydroquinoline-2,4′-piperidines]

It was established that the yields of a 4-allyl-4-aryl-aminopiperidines in the reaction of 4-aryliminopiperidines with allylmagnesium bromide increase significantly if the reaction is carried out in the presence of a crown ether. A number of previously unknown spiro[tetrahydroquinoline-2,4′-piperidines] were obtained in the cyclization of 4-allyl-4-arylaminopiperidines in the presence of sulfuric acid.