催化法双烯加成制取乙氧基二氢吡喃

报道了使用路易斯酸催化丙烯醛和乙烯基乙醚之间的 Diels-Alder 反应,反应条件为常温常压,其中以氯化锌及碘化锌结果最好,产品2-乙氧基-3,4-二氢-2H-呲喃收率在80%以上。求得无催化剂及以氯化锌作催化剂时的反应活化能,分别为51.3及8.3千焦/摩尔。实验表明该催化反应级数仍为二级.探讨了影响收率的主要因素,可能是由于环加成产品进一步开环聚合所致.

Synthesis of 2-ethoxy-3,4-dihydro-2H-pyran by Catalyzed Diels-Alder Reaction

The catalytic Diels-Alder reaction between acrolein and ethyl vinyl ether wascarried out in the presence of Lewis acid.The reaction conditions could be chan-ged from about 200℃ in an autoclave to ambient temperature and pressure.Thecatalytic activities of zinc chloride and zinc iodide were the highest among allcatalysts tested.The yield of 2-ethoxy-3,4-dihydro-2H-pyran was over 80%.The activation energies of the reaction in the absence of catalyst and in thepresence of zinc chloride were 51.3 and 8.3kJ/mol respectively.From the expe-rimental results it is shown that the catalytic reaction is of the second orderjust as that of the noncatalytic ones.The main factor affecting the productyield was investigated which was probably the further ring opening polymeriza-tion of the cycloaddition product.