生成和捕获缺电子 1,2-环己二烯。出乎意料的杂 Diels-Alder 反应性。
Generation and trapping of electron-deficient 1,2-cyclohexadienes. Unexpected hetero-Diels-Alder reactivity.
机构信息
Department of Chemistry, University of Alberta, E3-43 Gunning-Lemieux Chemistry Centre, Edmonton, AB, Canada T6G 2G2.
Department of Chemistry, University of Manitoba, 360 Parker Bldg., 144 Dysart Rd., Winnipeg, MN, Canada R3T 2N2.
出版信息
Org Biomol Chem. 2021 Jan 21;19(2):399-405. doi: 10.1039/d0ob02285c.
Keto-substituted 1,2-cyclohexadienes were generated by base-mediated (KOt-Bu) elimination, and found to dimerize via an unprecedented formal hetero-Diels-Alder process, followed by hydration. These highly reactive cyclic allene intermediates were also trapped in Diels-Alder reactions by furan, 2,5-dimethylfuran, or diphenylisobenzofuran to afford cycloadducts with high regio- and diastereoselectivity, and could also be intercepted in a hetero-Diels-Alder process with enamine dienophiles. Endo/exo stereochemistry was unambiguously determined via X-ray crystallography in the case of nitrile-substituted 1,2-cyclohexadiene. DFT calculations indicate that the novel hetero-Diels-Alder processes observed with these allenes occur via a concerted asynchronous cycloaddition mechanism.
酮取代的 1,2-环己二烯通过碱介导（KOt-Bu）消除生成，并通过前所未有的形式杂 Diels-Alder 过程发现二聚，随后进行水合。这些高反应性的环状丙二烯中间体还可以通过呋喃、2,5-二甲基呋喃或二苯并呋喃与 Diels-Alder 反应捕获，以高区域和立体选择性得到环加成产物，也可以与烯胺二烯试剂在杂 Diels-Alder 过程中被拦截。腈取代的 1,2-环己二烯的情况通过 X 射线晶体学明确确定了内/外立体化学。DFT 计算表明，与这些丙二烯观察到的新型杂 Diels-Alder 过程通过协同异步环加成机制发生。
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