| 摘要 |
The present invention relates to a process for the preparation of ²-ionones and/or ±-ionones of the formulae II and III
by acid catalyzed ring-closing of È-ionones of the formula I
wherein R 1 to R 7 are independently selected from hydrogen and C 1 -C 4 -alkyl, R 8 is selected from hydrogen and C 1 -C 4 -alkyl and the hydroxyl group, R 9 and R 10 are independently selected from hydrogen and C 1 -C 4 -alkyl or R 9 and R 10 form together the oxygen of a carbonyl group, whereby if R 9 and R 10 form together the oxygen of a carbonyl group no ±-isomer is formed comprising:
a) reacting a È-ionone according to formula I in presence of a concentrated Brønsted-acid having a pKs < 3, and an organic solvent that is substantially immiscible with the concentrated acid and with an diluted aqueous solution of said acid;
b) hydrolysis of the reaction product obtained in step a) by addition of water; and phase separation into an organic phase comprising the ²-ionone and/or the ±-ionone of the formulae II and III and into an aqueous diluted acid phase;
wherein water is added in the hydrolysis step b) in an amount to achieve an acid concentration in said aqueous diluted acid phase of 45 to 65 wt-%, that also can be easily integrated in a process for the preparation of vitamin A, a vitamin A derivative, a carotene or a carotenoid.
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