In a 100 mL round bottom flask, 2 g of (R)-3-hydroxypyrrolidine, 25 mL of tetrahydrofuran (THF), 0.49 g of paraformaldehyde, and 1.5 g of 90% formic acid were added sequentially. The reaction mixture was stirred under reflux conditions for 5 h (until all solids were completely dissolved), after which the reaction system was cooled to 0 °C and the pH was adjusted to about 10 by slow addition of 10 mL of 10 N sodium hydroxide solution. the organic phase was separated and dried over anhydrous magnesium sulfate. After filtration to remove the desiccant, the solvent (THF) was removed by distillation under reduced pressure to afford the oily product (R)-1-methyl-3-hydroxypyrrolidine (1.5 g, 92% yield). The product was characterized by 1H NMR (CDCl3, 300 MHz): δ 1.50-1.60 (m, 1H), 1.98-2.10 (m, 1H), 2.25 (s, 3H), 2.25-2.40 (m, 2H), 2.50-2.60 (m, 1H), 2.61-2.70 (m, 1H), 3.80 (brs, 1H), and 4.20-4.30 (m, 1H).
