Solid-Phase Synthesis of Dihydropyrans by Eu(fod)3-Catalysed [4+2] Heterocycloaddition of Vinyl Ethers with Benzylidenepyruvic Acid Esters. Comparison with Conventional Homogeneous Liquid Phase Conditions
作者:Stéphane Leconte、Gilles Dujardin、Eric Brown
DOI:10.1002/(sici)1099-0690(200002)2000:4<639::aid-ejoc639>3.0.co;2-6
日期:2000.2
resin were esterified with benzylidenepyruvic acid (1) to give the immobilized 1-oxabutadiene 2. The latter reacted with vinyl ethers 3a-h (dienophiles) in the presence of Eu(fod)3, and the resulting adducts 4a-h underwent reductive cleavage with LiAlH4 to afford the dihydropyrans 5a-h in high (62 to 100%) overall yields. A similar sequence carried out under conventional homogeneous liquid phase conditions
将Wang树脂的OH基与亚苄基丙酮酸(1)酯化,得到固定化的1-氧杂丁二烯2。后者在Eu(fod)3存在下与乙烯基醚3a-h(亲二烯体)反应,生成的加合物4a - h与LiAlH 4进行还原裂解,得到高浓度(62%至100%)的二氢吡喃5a-h。整体产量。在常规均相液相条件下进行的类似步骤导致产率大大降低。在两种情况下,环加成反应的内/外选择性相同。