COHALOGENATION OF ALKENES IN ETHYLENE-OXIDE - EFFICIENT METHODOLOGY FOR THE PREPARATION OF ALLYL VINYL ETHER PRECURSORS OF GAMMA,DELTA-UNSATURATED ALDEHYDES

An investigation of the cohalogenation-dehydrohalogenation sequence as a method for the preparation of allyl vinyl ethers from simple olefin s has been performed. Alkenes 1a-k react with bromine or chlorine in t he presence of ethylene oxide at -80-degrees-C to form beta,beta'-diha lo ethers 2a-k regio- and stereoselectively in high yields. Two of the se beta,beta'-dihalo ether intermediates were selectively mono-dehydro halogenated by potassium tert-butoxide to give 2-haloalkyl vinyl ether s in almost quantitative yields. Use of an excess of base produces all yl vinyl ethers 3a-k in good yields. Thermal rearrangement of the latt er converts them into the corresponding gamma,delta-unsaturated aldehy des 4a-j.