a unique process for preparing certain hexahydroaroquinolizines , especially - n -- quinolizine - 2 , 4 &# 39 ;- imidazolidin ]- 3 &# 39 ;- yl ) ethyl )- methanesulfonamide from - n - quinolizin - 2 - yl ) amino ] ethyl ] methanesulfonamide is described .