A 35% aqueous formaldehyde solution (16.07 mL, 187.3 mmol, 3.0 eq.) was mixed with potassium bicarbonate (0.53 g, 5.27 mmol, 0.08 eq.) in a 20 °C water bath. Diethyl malonate (10.00 g, 62.43 mmol, 1.0 eq.) was added slowly and the reaction mixture was stirred overnight. After completion of the reaction, saturated sodium sulfate solution was added and the product was extracted with ether. The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give the crude product diethyl 2,2-bis(hydroxymethyl)malonate (13.79 g, 100%) as a clear colorless oil. The product could be used in the next reaction without further purification. Thin layer chromatography (TLC) Rf value was 0.31 (unfolding agent: 50% ethyl acetate/hexane). IR spectrum (neat, cm-1): 3433 (O-H), 2982 (C-H), 1790 (C=O), 1209, 1028. 1H NMR (300 MHz, CDCl3): δ 4.22 (q, 4H, J = 6.7 Hz, 2 × OCH2CH3), 4.09-4.04 (m, 4H, 2 × CH2OH), and 2.99 (s, 2H, 2 × OH), 1.25 (t, 3H, J = 7.1 Hz, OCH2CH3), 1.24 (t, 3H, J = 7.1 Hz, OCH2CH3).13C NMR (75 MHz, CDCl3): δ 169.58, 63.54, 61.97, 61.21, 14.04.
