2-Nitrophenol → Carvone, (-)-

Participants

Reaction Conditions

Reaction Steps

A mixture of 600 parts of R-(+)-1,2-limonene oxide, 5.7 parts of 2-nitrophenol and 12 parts of zinc carbonate was refluxed at 202-227° C. for 7 hours in a three-necked flask equipped with agitator, 3-foot distillation column, distillation head, temperature probe, and addition funnel. When the rearrangement step was completed (no 1,2-limonene oxide left in the reaction mixture), 190 parts of cyclohexanone were slowly added to the reaction mixture. The mixture was held at reflux for 2 hours at 195-200° C. and then cooled down to 120° C. The mixture of cyclohexanone and cyclohexanol was removed at 10-15 mm Hg and pot temperature below 120° C. Cyclohexanone addition step followed by reflux and removal of cyclohexanone-cyclohexanol mixture under vacuum was repeated two more times. After the oxidation step was completed, the conversion of R-(−)-carveol to R-(−)-carvone was above 95%. The catalyst was removed by filtration, and the filtrate was distilled to afford 473 parts of 80% pure R-(−)-carvone (theory yield 63% on 1,2-limonene oxide). This material was purified using conventional methods to 99.6% pure flavor grade R-(−)-carvone.

Provenance & Evidence