College of Chemistry and Molecular Sciences, Wuhan University , Wuhan 430072, China.
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry , Shanghai 230012, China.
Org Lett. 2017 Mar 3;19(5):1176-1179. doi: 10.1021/acs.orglett.7b00215. Epub 2017 Feb 17.
Unprecedented PPh-mediated [4 + 2]- and [4 + 1]-annulation of maleimides with in situ formed azoalkenes have been successfully developed, affording fused tetrahydropyridazine/pyrrolidinedione and spiro-dihydropyrazole/pyrrolidinedione derivatives in good yields under mild reaction conditions. Maleimides serve as C2 synthons in the [4 + 2]-annulation using 1,2-dichloroethane as the solvent in the presence of 20 mol % of PPh. With a stoichiometric amount of PPh in acetone, maleimides serve as C1 synthons, and the in situ formed phosphorus ylide is the key intermediate to realize this [4 + 1]-annulation.
在温和的反应条件下，通过亚胺与原位生成的重氮烯烃的前所未有的 PPh 介导的 [4 + 2]-和 [4 + 1]-环加成反应，成功地合成了稠合的四氢嘧啶/吡咯二酮和螺二氢吡唑/吡咯二酮衍生物，产率良好。在 20 mol %的 PPh 的存在下，使用 1,2-二氯乙烷作为溶剂，马来酰亚胺作为 C2 合成子参与 [4 + 2]-环加成反应。在丙酮中，当 PPh 的量为化学计量时，马来酰亚胺作为 C1 合成子，原位形成的磷叶立德是实现这一 [4 + 1]-环加成反应的关键中间体。
