Sulfuric Acid → Diacetone L-sorbose

Participants

Reaction Conditions

Reaction Steps

24 mL of sulfuric acid were added dropwise, with vigorous stirring, to 100 mL of acetone cooled to 0-5° C., at a rate such that the reaction temperature remained below 20° C. 5 g of L-sorbose were added to the reaction mixture, and stirring was allowed to continue for 4 h at room temperature. The reaction mixture was allowed to stand at room temperature overnight, and was cooled to -8° C. (ice-NaCl bath). The cooled reaction mixture was neutralized to pH 8 with saturated NaHCO3 at a rate such that the reaction temperature remained below 0° C. The resulting mixture containing precipitated Na2SO4 was allowed to warm to room temperature and the Na2SO4 was filtered and washed twice with dry acetone. Combined organic filtrate and washings were concentrated in vacuo at 20° C., and the resulting oily residue was extracted with chloroform (5×10 mL). The chloroform extract was dried (MgSO4) and evaporated to afford a viscous gum which crystallized (mp.=59-61° C.) upon standing. Recrystallization (benzene) of the above crystallized gum afforded 4.8 g (67%) of the above-titled compound as fine crystals: mp.=76-77° C. (lit. 77-78° C. (T. Reichstein et al., Helv. Chim. Acta, 1934, 17, 331); 1H NMR (CDCl3) δ1.35 (s, 6H), 1.45 (s, 3H), 1.52 (s, 3H), 2.50 (br. s, 1H, OH), 3.75-3.90 (m, 2H, 6-H2), 4.05-4.15 (m, 3H), 4.33 (d, 1H, 3H), 4.5 (d, 1H, J≈1H, 1-H).

Provenance & Evidence