Diels-Alder reactions of ethyl (E)-3-(1, 3-benzothiazol-2-yl)-3-cyanopropenoate (2) as a 1-aza-1, 3-butadiene are described. The diene (2), bearing electron-withdrawing ester group, reacts with electron-rich dienophiles (3a-d) under extremely mild conditions to give corresponding cycloadducts (4a-d) in high yields with high regio- and endo-selectivities. Treatment of 2 with electron-donating allyl alcohols (5a, b) causes tandem transesterification and intramolecular cycloaddition to afford cis-fused polycyclic systems (6a, b) in one step.
以乙基(E)-3-(1,3-
苯并噻唑-2-基)-3-
氰基丙烯酸酯(2)作为1-氮杂-
1,3-丁二烯,描述了其Diels-Alder反应。含有电子吸引性酯基的二烯(2)在极其温和的条件下与富电子的亲二烯体(3a-d)反应,以高产率、高区域选择性和endo选择性得到相应的环加成产物(4a-d)。将2与供电子的
烯丙醇(5a,b)作用会引发酯交换和分子内环加成串联反应,一步生成顺式并环多环体系(6a,b)。