| 摘要 |
<p>PURPOSE:To prepare alpha-ionones containing a large amount of gamma-ionones and having unique flavor, in high efficiency, by cyclizing pseudoionones in the presence of a phosphoric acid catalyst in a polar aprotic solvent. CONSTITUTION:A catalyst composed of 85% phosphoric acid is mixed with a polar aprotic solvent. Pseudoionones (a mixture of cis-and trans-isomers) of formula I (R1 and R2 are H or lower alkyl), e.g. 6,10-dimethylundeca-3,5,9-trien-2-one (pseudoionone), is dissolved in an inert organic solvent such an n-hexane, and cyclized by adding the mixture prepared above to the solution at 50-150 deg.C to obtain ionones of formula V consisting of alpha-isomer (formula II), beta-isomer (formula III) and gamma- isomer (formula IV). Under the optimum condition, the content of the gamma-isomer in the product reaches to 16%. The polar aprotic solvent is an aprotic solvent having a dielectric constant of >=15 and a dipole moment of >=25D, pref. N,N-dimethylformamide, N,N-dimethylacetamide, etc.</p> |
