An investigation of the cohalogenation-dehydrohalogenation sequence as a method  for the preparation of allyl vinyl ethers from simple olefins has been  performed. Alkenes 1a-k react with bromine or chlorine in the presence of  ethylene oxide at - 80°C to form β,β′-dihalo ethers 2a-k regio- and  stereoselectively in high yields. Two of these β,β′-dihalo ether  intermediates were selectively monodehydrohalogenated by potassium tert-butoxide  to give 2-haloalkyl vinyl ethers in almost quantitative yields. Use of  an excess of base produces allyl vinyl ethers 3a-k in good yields. Thermal  rearrangement of the latter converts them into the corresponding  γ,δ- unsaturated aldehydes 4a-j.
                                    对卤素共
氟化-脱卤化顺序作为从简单烯烃制备烯丙基
乙烯醚的方法进行了研究。烯烃1a-k在-80°C下与
溴或
氯在
环氧乙烷的存在下反应, regio-和立体选择性地形成高产率的β,β′-二卤醚2a-k。这些β,β′-二卤醚中有两个经过选择性单脱卤化处理,使用
叔丁醇钾生成几乎定量的2-卤烷基
乙烯醚。使用过量的碱可生成良好产率的烯丙基
乙烯醚3a-k。后者的热重排将其转化为相应的γ,δ-不饱和醛4a-j。