Into a 12-L flask equipped with magnetic stirring, addition funnel, temperature probe, and nitrogen inlet was charged 0.460 kg ethyl 2-(4-methoxyphenyl)-4-(3,4-methylenedioxyphenyl)-4,5-dihydro-3H -pyrrole-3-carboxylate (1.25 mol). The reaction vessel was degassed with nitrogen. Absolute 3.7 L ethanol and 1.12 L of THF were added. 31 mg bromocresol green and 94.26 g sodium cyanoborohydride (1.5 mol) were added. A solution containing 400 mL absolute ethanol and 200 mL of 12M HCl was then added. The reaction mixture was stirred for 30 minutes after addition was complete. After the starting material was consumed, 0.5 L of 7% aq. NaHCO3 was added. The reaction mixture was concentrated and diluted with 5 L ethyl acetate. The organic layer was washed twice with 2 L of 7% aq. NaHCO3 and once with 2.5 L of 23% aq. NaCl, the dried over 190 g MgSO4, filtered, and concentrated to give 447 g of the title compound as a thick yellow oil.
