Formaldehyde → (S)-Methyl 1-methylpyrrolidine-2-carboxylate

A 10.42 g (62.92 mmol) sample of L-proline methyl ester hydrochloride (Aldrich Chemical Co.) was reductively methylated over 2.5 g of 10% Pd/C under 4 Atm of hydrogen in a solution containing 20 g of sodium acetate and 49.5 mL of 37% aqueous formaldehyde for 48 hours. Upon completion of the reaction, the methanolic solution was concentrated and the residue was dissolved in 10% aq. HCl (60 mL) and washed with ether (3×100 mL), then the aqueous layer was adjusted to pH ~12 with K2CO3 (solid) and extracted with methylene chloride (3×75 mL). The combined methylene chloride layers were dried (MgSO4) and concentrated to afford the crude product as a clear oil (16.6 g, 77% yield).