Process for stereoselectively synthetizing cyclopropane carboxylates as intermediates for pyrethroids
申请人:Montedison S.p.A.
公开号:EP0043143A2
公开(公告)日:1982-01-06
Stereoselective process for preparing lower alkyl esters of the cis-2,2-dimethyl-3-(β-trifluoromethyl-β- fluorovinyl)-cyclopropane carboxylic acid of formula:
(wherein R = an alkyl C,-C4) in which a compound of formula:
(wherein R has the meaning specified hereinabove and substituent Y is an atom of chlorine' or of bromine) is monodehydrohalogenated in the presence of a primary or secondary amine and in an apolar solvent or in a low-polarity solvent, so selectively obtaining a compound of formula:
(wherein Y and R have the meanings specified hereinabove), which, in its turn, is dehydrohalogenated by the action of an alkaline base in an apolar solvent or in ether maintaining, in the latter case, a temperature below 50°C.
The compounds thus obtained are intermediates for the preparation of pyrethroids.
制备式为顺式-2,2-二甲基-3-(β-三氟甲基-β-氟乙烯基)-环丙烷羧酸的低级烷基酯的立体选择性工艺:
(其中 R = C,-C4烷基)的式化合物:
(其中 R 具有上述含义,取代基 Y 为氯原子或溴原子)在伯胺或仲胺存在下,在无 极溶剂或低极性溶剂中进行单脱氢卤化,从而选择性地获得式化合物: (其中 Y 和 R 具有上述含义,取代基 Y 为氯原子或溴原子):
(式中 Y 和 R 的含义见下文),然后在碱性碱的作用下,在无极性溶剂中或在乙醚中(后一种 情况下温度保持在 50℃以下)进行脱氢卤化。
由此得到的化合物是制备拟除虫菊酯的中间体。