2.2.3. Synthesis of 5-methyl-1,3-dioxolan-4-one (LA-H,H)

For the synthesis of LA-H,H we followed the procedure reported by Cairns et al. [40] with the following modifications.

Here, 45.0 g of DL-lactic acid (0.500 mol), 22.5 g of paraformaldehyde (0.750 mol), 300 mL of petroleum ether (bp: 60–80 ◦C) and 1.5 g of *p*TsOH (0.0080 mol) as a Brønsted acid catalyst were added in a 500 mL round-bottom flask equipped with a 25 mL Dean-Stark trap and Allihn condenser. The reaction was refluxed under vigorous magnetic stirring for 24 h. After reaction time, the crude mixture was cooled in an ice bath and treated with 3.0 g of Na2CO3 (0.035 mol) for 30 min. The reaction crude was then filtered, and volatile solvent evaporated under reduced pressure. The product was isolated by vacuum distillation (15 mbar) at 45–47 ◦C. 1H NMR (400 MHz, CDCl3) δ 5.51 (s, 1H), 5.38 (s, 1H), 4.27 (q, J = 6.8, 1H), 1.47 (d, J = 6.8, 3H).
