lithium aluminium tetrahydride in diethyl ether T=0°C; 2 h;

borane; tetrabutyl ammonium fluoride; (S)-CBS-oxazaborolidine 1.) THF, 25 deg C, 1 h 10 min, 2.) THF, MeOH, room temp., 1 h; Yield given. Multistep reaction;

1.1: NaH / tetrahydrofuran / 0.5 h / 20 °C 1.2: 85 percent / tetrahydrofuran / 2 h 2.1: 91 percent / diisobutylaluminum hydride / CH2Cl2; hexane / 1 h / -20 °C View Scheme

With  diisobutylaluminium hydride; (S)-1-methyl-2-lt;(piperidin-1-yl)-methylgt;pyrrolidine; tin(ll) chloride in  dichloromethane T=-100°C; 0.333333 h;  Yield given. Title compound not separated from byproducts;   

With  diisobutylaluminium hydride; (S)-1-methyl-2-lt;(piperidin-1-yl)-methylgt;pyrrolidine; tin(ll) chloride in  dichloromethane T=-100°C; 0.333333 h;  Yield given. Title compound not separated from byproducts;