with alcohols is accompanied by the second pathway, giving rise to, for example, (Z)-4 b in addition to (E)-6 b. Phenol engages in the third pathway and provides (E)-6 g exclusively. Heteroaromatics, such as furans and benzofurans follow the first pathway, however, in a different regioselectivity from enol ethers and allylsilanes, delivering the oxygen atom at the 3-position of 5-sulfonyltetrahydropyridines
丙二烯氨基甲酸酯1的Calpha == Cbeta双键通过与N-SO2键的空间相互作用,充当与共轭烯酮的双键相似的电子受体。因此,
氨基甲酸酯双键会经历多种亲核试剂的亲核加成反应,在温和条件下通过加热至70-100摄氏度进行。1根据亲核试剂的种类,1显示三种不同的反应模式:1)典型的烯醇醚烯丙基
硅烷可促进1的1,3-磺酰基迁移,并与1-氮杂-
1,3-丁二烯中间体II发生电子反需求Diels-Alder反应,从而形成双环2-烷氧基-5-磺酰基四氢
吡啶2和2-甲
硅烷基甲基-5-磺酰基四氢
吡啶3 具有高的区域和立体选择性,并保留了这些富电子烯烃的双键的构型;2)
硅烷(RnSiH4-n,n = 1-3)和
硫醇在Cbeta碳处传递
氢化物和
硫醇盐并促进1,3-磺酰基迁移,随后将如此形成的
氨基甲酸酯阴离子(Z)质子化- III分别提供例如(Z)-4a和(Z)-4j;3)醇仅加至Calpha == Cbet