申请人:NAARDEN INTERNATIONAL N.V.
公开号:EP0325000A1
公开(公告)日:1989-07-26
The invention provides a process for the preparation of 5,6-dihydro-2H-pyran derivatives, wherein an aldehyde of formula I:
wherein R₁ represents an alkyl, cycloalkyl, aralkyl, alkaryl or aryl group having at most 15 carbon atoms and a diene of formula II:
wherein R₂ and R₃ represents a hydrogen atom or an alkyl group having 1-6 carbon atoms are reacted in a Diels-Alder-type reaction under the influence of an inorganic Lewis acid catalyst, producing a compound of formula III wherein R₁-R₃ have the meaning given above.
Preferably R₁ represents a 1-6 carbon atom alkyl group, a phenyl group or an o-, m- p-tolyl group. Isoprene or 2-methyl-1,3-pentadiene is preferably used as the diene. The preferred catalyst is AlCl₃ or SnCl₄ and an organic nitro compound may be used as the co-catalyst.
本发明提供了一种制备 5,6-二氢-2H-吡喃衍生物的工艺,其中式 I 的醛:
其中 R₁代表具有至多 15 个碳原子的烷基、环烷基、芳基、烷芳基或芳基和式 II:
其中 R₂ 和 R₃ 代表氢原子或具有 1-6 个碳原子的烷基,在无机路易斯酸催化剂的作用下进行 Diels-Alder 型反应,生成式 III 的化合物,其中 R₁-R₃ 具有上述含义。
R₁ 最好代表 1-6 个碳原子的烷基、苯基或邻、间、对甲苯基。异戊二烯或 2-甲基-1,3-戊二烯最好用作二烯。优选催化剂为 AlCl₃或 SnCl₄,有机硝基化合物可用作助催化剂。