Department of Chemistry, Center for Molecular Discovery (BU-CMD), Life Science and Engineering Building, Boston University , 24 Cummington Mall, Boston, Massachusetts 02215, United States.
Org Lett. 2017 Apr 7;19(7):1878-1881. doi: 10.1021/acs.orglett.7b00647. Epub 2017 Mar 30.
Iron(III) salts promote the condensation of aldehydes or acetals with electron-rich phenols to generate ortho-quinone methides that undergo Diels-Alder condensations with alkenes. The reaction sequence occurs in a single vessel to afford benzopyrans in up to 95% yield. The reaction was discovered while investigating a two-component strategy using 2-(hydroxy(phenyl)methyl)phenols to access the desired ortho-quinone methide in a Diels-Alder condensation. The two-component condensation also afforded the corresponding benzopyran products in yields up to 97%. Taken together, the two- and three-component strategies using ortho-quinone methide intermediates provide efficient access to benzopyrans in good yields and selectivities.
铁(III)盐促进醛或缩醛与富电子苯酚的缩合,生成邻醌甲醚,后者与烯烃发生 Diels-Alder 缩合。该反应序列在单个容器中进行,以高达 95%的收率生成苯并吡喃。该反应是在研究使用 2-(羟苯基)甲基)苯酚的二组分策略时发现的,该策略用于在 Diels-Alder 缩合中获得所需的邻醌甲醚。二组分缩合也以高达 97%的收率得到相应的苯并吡喃产物。总之,使用邻醌甲醚中间体的二组分和三组分策略为苯并吡喃的高产率和选择性提供了有效的途径。