Process for producing 4-hydroxycyclopentenones

A method of producing a 4-hydroxycyclopentenone represented by the formula, ##STR22## wherein R.sub.1 is an alkyl, alkenyl, alkynyl, cycloalkyl, thienyl, phenyl, p-methylbenzyl or benzyl group and R.sub.2 is an alkyl, alkenyl or alkynyl group having 6 or less carbon atoms, which comprises oxidizing a cyclopentenone compound of the formula, ##STR23## wherein R.sub.1 is as defined above, in the presence of an oxidizing agent selected from the group consisting of chromic anhydride, chromates, dichromic acid, dichromates, chromyl chloride, chromate esters, chromic oxide-pyridine complex, manganese dioxide, activated manganese dioxide, potassium permanganate, aluminum isopropoxide, aluminum tert-butoxide, lead tetraacetate, ruthenium tetraoxide, N-halocarboxylic acid amide, oxygen, hydrogen peroxide, organic peroxides, halogen, nitric acid, nitrous acid, dimethyl sulfoxide, quinones, silver (I) carbonate, silver (II) carbonate, copper (II) oxide, copper (II) hydroxide, cerium (IV) salts, vanadates, cobalt (II) salts and ozone, at -20.degree. to 180.degree. C., to obtain a cyclopentendione compound of the formula, ##STR24## wherein R.sub.1 is as defined above;

• reacting the cyclopentendione compound with a Grignard reagent of the formula,
• R.sub.2 MgX
• wherein R.sub.2 is as defined above and X is chlorine, bromine or iodine, to obtain an oxocyclopentene compound of the formula, ##STR25## wherein R.sub.1 and R.sub.2 are as defined above;
• and reacting the oxocyclopentene compound in the presence of a base selected from the group consisting of hydroxides, carbonates, bicarbonates and acetates of sodium and potassium;
• basic salts of hydroxides, carbonates, bicarbonates and acetates of calcium and barium;
• triethylamine or pyridine;
• and basic ion exchange resins;
• in an amount of from 0.01 to 10 moles per mole of the oxocyclopentene compound at 0.degree. to 200.degree. C., or in the presence of alumina in an amount of from 0.5 to 30 times the weight of the oxocyclopentene compound at 0.degree. to 150.degree. C.

A method of producing a 4-hydroxycyclopentenone represented by the formula, ##STR26## wherein R.sub.1 is an alkyl, alkenyl, alkynyl, cycloalkyl, thienyl, phenyl, p-methylbenzyl or benzyl group and R.sub.2 is an alkyl, alkenyl or alkynyl group having 6 or less carbon atoms, which comprises reacting a furylcarbinol compound of the formula, ##STR27## wherein R.sub.1 is as defined above, in the presence of an acid selected from the group consisting of formic acid, trichloroacetic acid, dichloroacetic acid, phosphoric acid, polyphosphoric acid and pyrophosphoric acid, in a mixed solvent of water and an organic solvent selected from the group consisting of acetone, dioxane, methyl ethyl ketone, tetradyrofuran and dimethyl sulfoxide, to obtain a cyclopentenone compound of the formula, ##STR28## wherein R.sub.1 is as defined above;

• oxidizing the cyclopentenone compound in the presence of an oxidizing agent selected from the group consisting of chromic anhydride, chromates, dichromic acid, dichromates, chromyl chloride, chromate esters, chromic oxide-pyridine complex, manganese dioxide, activated manganese dioxide, potassium permanganate, aluminum isopropoxide, aluminum tert-butoxide, lead tetraacetate, ruthenium tetraoxide, N-halocarboxylic acid amide, oxygen, hydrogen peroxide, organic peroxides, halogen, nitric acid, nitrous acid, dimethyl sulfoxide, quinones, silver (I) carbonate, silver (II) carbonate, copper (II) oxide, copper (II) hydroxide, cerium (IV) salts, vanadates, cobalt (II) salts and ozone, at -20.degree. to 180.degree. C., to obtain a cyclopentendione compound of the formula, ##STR29## wherein R.sub.1 is as defined above;
• reacting the cyclopentendione compound with a Grignard reagent of the formula,
• R.sub.2 MgX
• wherein R.sub.2 is as defined above and X is chlorine, bromine or iodine, to obtain an oxocyclopentene compound of the formula, ##STR30## wherein R.sub.1 and R.sub.2 are as defined above;
• and reacting the oxocyclopentene compound in the presence of a base selected from the group consisting of hydroxides, carbonates, bicarbonates and acetates of sodium and potassium;
• basic salts of hydroxides, carbonates, bicarbonates and acetates of calcium and barium;
• triethylamine or pyridine;
• and basic ion exchange resins;
• in an amount of from 0.01 to 10 moles per mole of the oxocyclopentene compound at 0.degree. to 200.degree. C., or in the presence of alumina in an amount of from 0.5 to 30 times the weight of the oxocyclopentene compound at 0.degree. to 150.degree. C.