Process for producing and purifying 3,4-dihydrocoumarin.

摘要

A 3-(2-cyclohexanoyl)propionic acid ester is in the presence of a solid metallic catalyst, cyclized and dehydrogenised at 100 DEG to 350 DEG C, optionally with solvent and promotor to given 3,4-dihydrocoumarin [D] in 30-70 mol% yield and coumarin [C] 5-35 mol% and by-product dihydrocinnamic acid [A], 0.1-20 wt%; hydrogenation can convert [C] to [D]. The reaction mixture is purified by (i) to remove acidic compounds washing with an aqueous solution of an alkali (e.g., NaOH or NAHCO3); if a strong alkali metal or alkaline earth hydroxide is used its amount is not more than 1.5 equivalent per equivalent of [D]; the amount of solution is 0.1 to 10 times by weight that of the reaction mixture. The washing reduces the content of [A] to 1% by weight of the weight of [D], and/or (ii) to remove high boiling o-ethylphenyl cyclohexylpropionate/dihydrocinnamate to 2% by weight of that of [D] distillation at a reflux ratio of not more than 5 or in a tower having 10 stages or less, at 13-13330 Pa (0.1 to 10 Torr); (i) and (ii) can be used together in either order, followed by rectification in a 5-100 stage tower at a reflux ratio of 1 to 50, to recover [D]. The product contains not more than 0.05% of [A] and is suitable for use in perfume.