Sulfuric Acid → Ethanedioic acid, 1,2-bis[(1R,2S,5R)-5-methyl-2-(1-methylethyl)cyclohexyl] ester, rel-

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Reaction Steps

Oxalyl chloride (12.1 g, 96.2 mmol) was added dropwise during 20 min to a stirred solution of (−)-menthol (30.0 g, 192.0 mmol) in pyridine (240 mL) at 0° C. The reaction mixture was allowed to warm up to room temperature overnight, then added to H2SO4 (50%, containing ice, 400 mL), extracted with ether (400 mL and 200 mL), treated again with H2SO4 (50%, containing ice, 400 mL), washed with a saturated solution of NaCl (200 mL) and a saturated solution of NaHCO3 (200 mL, 2×). The organic layer was dried (Na2SO4) and concentrated. Column chromatography (SiO2, heptane/diethyl ether 9:1) gave, after drying under vacuum (0.5 mbar, 1 h), 26.2 g (74%) of an oil.

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