The solution of 8.0 g of 1-methyl-3-acetonyl-4-(3-methoxyphenyl)-1,5,6,7-tetrahydro-2H-azepinone, 14.2 g of piperidine, 6.4 ml of 5 N methanolic hydrogen chloride and 1.91 g of sodium cyanoborohydride in 100 ml of methanol is refluxed overnight. An additional portion of 1.91 g of sodium cyanoborohydride is added and refluxing continued for another day. The solution is cooled, acidified with 35 ml of concentrated hydrochloric acid and evaporated. The residue is diluted with 100 ml of water, the aqueous solution washed with benzene, filtered, basified with 65 ml 3 N aqueous sodium hydroxide and extracted with diethyl ether. The extract is dried, evaporated and the residue crystallized from petroleum ether and recrystallized from hexane, to yield the 1-methyl-3-(2-piperidinopropyl)-4-(3-methoxyphenyl)-1,5,6,7-tetrahydro-2H-azepinone melting at 101°-103°.
