To a stirred solution of (S)-3-(1-carbamoyl-1,1-diphenylmethyl)pyrrolidine (64.4 g, 0.23 mol); sodium triacetoxyborohydride (50.9 g, 0.24 mol) and acetic acid (13 mL, 0.23 mol) in dichloromethane (511 mL) at room temperature, was added a solution of hex-5-yn-1-al (26.14 g, 0.27 mol) in dichloromethane (256 mL). The reaction mixture stirred at room temperature overnight (ca. 8 hours) and then the reaction mixture was quenched by addition of concentrated hydrochloric acid (30 mL) and stirring was continued for 1 hour at room temperature. The mixture was then diluted with water (750 mL) and made basic to pH 5 using 10 N sodium hydroxide (18 mL). The layers were separated and the organic layer was washed with 1 N sodium hydroxide (200 mL). The organic layer was dried over magnesium sulfate (10 g); filtered and then concentrated in vacuo to afford 67.6 g of the title intermediate as a yellow gummy solid (83% yield).
