OS([O-])(=O)=O.[Na+].O.[OH-].[Na+].[CH3:10][C@H:11]1[CH2:16][C@@H:15]([OH:17])[C@H:14]([C:18]([CH3:20])=[CH2:19])[CH2:13][CH2:12]1.OO.S([O-])([O-])=[O:24].[Na+].[Na+]>OP(O)(O)=O.O.C1(C)C=CC=CC=1>[CH3:10][C@H:11]1[CH2:16][C@@H:15]([OH:17])[C@H:14]([C:18]2([CH3:20])[O:24][CH2:19]2)[CH2:13][CH2:12]1Into a 500 mL 4 necked flask equipped with a stirrer and a reflux condenser, NaWO4·2H2O (6.60 g, 0.02 mol), NaHSO4·H2O (6.90 g, 0.05 mol), [(Oct)3MeN]Cl (4.04 g, 0.01 mol), 85% H3PO4 (0.98 g, 0.0085 mol), toluene (77 g) and water (10 g) were charged. After adjusting pH of the solution to 4.0 with a 20% NaOH aqueous solution (5.8 g), L-isopulegol (77.1 g, 0.5 mol) was added thereto, and a 30% H2O2 aqueous solution (85 g, 0.75 mol) was added drop-wise at a temperature in a range of 35 to 40° C. for 1.5 hours with stirring. After the reaction mixture was stirred at 40° C. for further 10 hours, a 20% sodium sulfite aqueous solution (161 g, 0.26 mol) was added drop-wise to the reaction liquid at 40° C. or lower with stirring. After left for standing, an organic layer was separated, and the resulting organic layer was washed twice with water (100 g), and then the solvent was distilled off under reduced pressure to obtain a crude epoxide (83.8 g). The epoxide was distilled with a Claisen distiller to obtain 71.0 g of isopulegol epoxide (GC purity: 95.6%, boiling point: 93° C./533 Pa). Yield was 83% based on isopulegol.
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