3-methyl-6-propan-2-ylidenecyclohex-2-en-1-one

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: sodium t-pentoxide, toluene; barium oxide, benzene; potassium t-butoxide, tetrahydrofuran; sodium hydride, tetrahydrofuran.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A 500 ml capacity autoclave was charged with 150 g (1 mol) of piperitenone, 18.6 mg (0.04 mmol) of [Rh(cod)2]PF6, 47.2 mg (0.04 mmol) of (S)-DIBM-SEGPHOS, 14.8 mg (0.02 mmol) of BrPPh3(CH2)4PPh3Br and 7.5 ml of ethyl acetate, and the reaction was carried out at 50° C. for 20 hours under a hydrogen pressure of 3 MPa. After completion of the reaction, hydrogen was purged, and the reaction solution was concentrated and distilled under a reduced pressure to obtain 136.8 g of d-pulegone (yield 90%). was purged the reaction solution was concentrated distilled under a reduced pressure

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 200 parts of 3,3-dimethylacrolein and 600 parts of tetrahydrofuran is heated with 0.008 part of p-toluenesulfonic acid in an autoclave for three hours at a pressure of 50 atmospheres and a temperature of 210°C. The reaction product is worked up by distillation. 72.5 parts of piperitenone is obtained. The yield is 78% of theory at a conversion of 52%. a temperature of 210°C The reaction product is worked up by distillation

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 200 parts of 3,3-dimethylacrolein, 600 parts of tetrahydrofuran and 1 part of formic acid is heated for 2 hours at a pressure of 120 atmospheres and a temperature of 280°C in an autoclave. The reaction product is worked up by distillation. 106 parts of piperitenone is obtained having a boiling point of 120° to 122°C at 14 mm Hg. The yield is 83% of theory at a conversion of 72%. is heated for 2 hours at a pressure of 120 atmospheres a temperature of 280°C The reaction product is worked up by distillation

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 70 g of methyl vinyl ketone are added dropwise in the course of 60 minutes, whilst stirring, to 1,000 g of mesityl oxide and 50 ml of 50% potassium hydroxide solution, at 70°C. Thereafter the mixture is stirred for a further 10 minutes at 70°C and neutralized with glacial acetic acid, and the organic phase is distilled. 181 g of crude piperitenone are obtained; piperitenone content 55.7%, yield therefore 67.2%. the organic phase is distilled

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The hydrogenation of the crude piperitenone is expediently carried out at temperatures at which as much d,l-menthol as possible is present in the menthol isomer mixture and no splitting off of water to form p-menthane takes place. Temperatures of 100° to 260°C, especially of 160° to 220°C, have proved advantageous.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A similar process is described by S. Ohshiro et al (Yakugaku Zasshi, 88, 417 (1968)). Here again the reaction of methyl vinyl ketone with excess mesityl oxide takes place in the presence of potassium hydroxide powder but without addition of tetrahydrofuran as the solvent. The piperitenone obtained is converted into a mixture of menthone and isomenthone by catalytic hydrogenation. However, in this process of yields of piperitenone are again only about 53%; furthermore, using this process the menthone/isomenthone mixture is obtained in only 64.6% yield and in a purity of only 89.8%. For this reason, the further reaction to give pure methol has to be carried out in an involved manner via menthone-oxime (Jap. Pat. No. 7,009,375) and menthylamine, which makes it doubtful whether the process is suitable for commercial operation.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A similar process is described by S. Ohshiro et al (Yakugaku Zasshi, 88, 417 (1968)). Here again the reaction of methyl vinyl ketone with excess mesityl oxide takes place in the presence of potassium hydroxide powder but without addition of tetrahydrofuran as the solvent. The piperitenone obtained is converted into a mixture of menthone and isomenthone by catalytic hydrogenation. However, in this process of yields of piperitenone are again only about 53%; furthermore, using this process the menthone/isomenthone mixture is obtained in only 64.6% yield and in a purity of only 89.8%. For this reason, the further reaction to give pure methol has to be carried out in an involved manner via menthone-oxime (Jap. Pat. No. 7,009,375) and menthylamine, which makes it doubtful whether the process is suitable for commercial operation.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Furthermore, J. J. Beereboom (U.S. Pat. No. 3,238,261 and J. Org. Chem., 31, 2026 (1966)) describes the reaction of methyl vinyl ketone with excess mesityl oxide in the presence of potassium hydroxide powder in tetrahydrofuran as the solvent. The piperitenone obtained is purified in a very expensive manner via the piperitenone-bisulfite adduct. In this process, yields of piperitenone of between 36 and 54% of theory are obtained.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A 500 ml capacity autoclave was charged with 150 g (1 mol) of piperitenone, 18.6 mg (0.04 mmol) of [Rh(cod)2]PF6, 47.2 mg (0.04 mmol) of (S)-DTBM-SEGPHOS, 14.8 mg (0.02 mmol) of BrPPh3(CH2)4PPh3Br and 7.5 ml of ethyl acetate, and the reaction was carried out at 50° C. for 20 hours under a hydrogen pressure of 3 Mpa. After completion of the reaction, hydrogen was purged, the reaction solution was concentrated and then distillation was carried out under a reduced pressure to obtain 136.8 g of pulegol. The yield was 90%. was purged the reaction solution was concentrated distillation

Conditions: temp:80.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A 688 ml (6.0 mol) portion of mesityl oxide was put into a one liter capacity four neck flask and mixed with 13.82 g (0.1 mol) of potassium carbonate and 2.28 g (10 mmol) of benzyltriethylammonium chloride, and the mixture was heated to 80° C. To this was added dropwise 166.48 ml (2.0 mol) of methyl vinyl ketone spending 1 hour while keeping at 80° C. After completion of the dropwise addition, this was stirred for 30 minutes and then the reaction solution was distilled under a reduced pressure to obtain 186 g of piperitenone. Yield 62%. while keeping at 80° C After completion of the dropwise addition the reaction solution was distilled under a reduced pressure

Conditions: temp:80.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A 688 ml (6.0 mol) portion of mesityl oxide was put into a one liter capacity four neck flask and mixed with 6.30 g (0.02 mol) of barium hydroxide octahydrate and 2.28 g (10 mmol) of benzyltriethylammonium chloride, and the mixture was heated to 80° C. To this was added dropwise 172 ml (2.0 mol) of 4-hydroxy-2-butanone spending 1 hour while keeping at 80° C. After completion of the dropwise addition, this was stirred for 30 minutes and then the reaction solution was distilled under a reduced pressure to obtain 182 g of piperitenone. Yield 62%. while keeping at 80° C After completion of the dropwise addition the reaction solution was distilled under a reduced pressure