ABSTRACT
Raney nickel* (1.5 g/1 mmol, from an aqueous suspension, Merck) was added at room temperature to a vigorously stirred solution of pyridine (5.7 mL/1 mmol), acetic acid (3.4 mL/1 mmol), and water (3.4 mL/1 mmol). Sodium hypophosphite† (0.74 g, 8.4 mmol), tosylhydrazine (0.20-0.32 g, 1.1-1.7 mmol), and the corresponding anhydro-aldononitrile 1 (1 mmol) were added to the mixture. The reaction mixture was stirred at room temperature (1b-e), while 1a was transformed at 40°C. When the reaction was complete (TLC, 1:1 ethyl acetate-hexane), the insoluble materials were ¥ltered off with suction and washed with dichloromethane (10 mL).‡ The organic layer of the ¥ltrate was separated, washed with water (3 mL), 10% aq. HCl (2 × 3 mL), cold, saturated aq. NaHCO3 (2 × 3 mL), water (3 mL), dried, and concentrated. Traces
of pyridine were removed by repeated co-evaporations with toluene. Chromatography (gradient elution, eluent: 1:2-1:1 ethyl acetate-hexane) gave 2a-d, while 2e was obtained by crystallization from ethyl acetate-hexane.
