2,5-bis(1,1-dialkoxy-2-propyl)-2,5-dihydrofurans, the preparation thereof and the use thereof for the preparation of carotenoids

摘要

2,5-bis(1,1-dialkoxy-2-propyl)-2,5-dihydrofurans of the formula I <IMAGE> (I) where R1 and R2 can be identical or different and can be alkyl of 1 to 4 carbons, the preparation thereof by reaction of 2,5-dialkoxy-2,5-dihydrofurans of the formula II <IMAGE> (II) In the presence of protic acids or Lewis acids with an alkyl propenyl ether of the formula III <IMAGE> (III) and the use thereof for preparing 2,7-dimethyl-2,4,6-octatrienedial and symmetric C40-carotenoids such as beta -carotene, canthaxanthin and astaxanthin, are described.