Department of Chemistry, Penn State Brandywine, 25 Yearsley Mill Road, Media, Pennsylvania 19063, USA.
J Org Chem. 2013 Sep 6;78(17):8614-23. doi: 10.1021/jo4012915. Epub 2013 Aug 15.
Reaction of 3-aminopyrrole with seven 1,3,5-triazines was studied in a one-step reaction (in situ formation of 3-aminopyrrole) and a two-step reaction (using the tetraphenylborate salt and an amine base). An inverse-electron demand Diels-Alder reaction (IEDDA) was observed with R1 = CF3, CO2Et, and H with the formation of 5H-pyrrolo[3,2-d]pyrimidine derivatives. S(N)Ar was observed when 2,4,6-trifluoro- or 2,4,6-trichloro-1,3,5-triazine were used--1,3,5-triazines that had leaving groups. If excess 1,3,5-triazine was present the initial S(N)Ar product reacted further, in the presence of acid and water, with another equivalent of 1,3,5-triazine to give compounds containing three linked heterocyclic rings. No reaction was observed with R1 = C6H5 and OCH3. Four mechanisms are proposed to explain the experimental results: uncatalyzed and acid catalyzed inverse electron demand Diels-Alder cascades leading to cycloaddition, and uncatalyzed and acid-catalyzed S(N)Ar reactions leading, respectively, to single and double substitution products. Acid catalysis was a factor when there was reduced reactivity in either reactant.
研究了 3-氨基吡咯与七种 1,3,5-三嗪的一步反应（原位形成 3-氨基吡咯）和两步反应（使用四苯硼酸盐盐和胺碱）。当 R1 = CF3、CO2Et 和 H 时，观察到逆电子需求 Diels-Alder 反应（IEDDA），形成 5H-吡咯并[3,2-d]嘧啶衍生物。当使用具有离去基团的 2,4,6-三氟-或 2,4,6-三氯-1,3,5-三嗪时，观察到 S(N)Ar--1,3,5-三嗪。如果存在过量的 1,3,5-三嗪，初始 S(N)Ar 产物会在酸和水的存在下进一步反应，与另一个当量的 1,3,5-三嗪反应，生成含有三个连接的杂环的化合物。当 R1 = C6H5 和 OCH3 时，没有反应。提出了四种机制来解释实验结果：无催化和酸催化的逆电子需求 Diels-Alder 级联反应导致环加成，以及无催化和酸催化的 S(N)Ar 反应分别导致单取代和双取代产物。当反应物的反应性降低时，酸催化是一个因素。
