Gold-Catalyzed Cyclization of 2-Alkynylaldehyde Cyclic Acetals via Hydride Shift for the Synthesis of Indenone Derivatives
作者:Tsuyoshi Yamada、Kwihwan Park、Takumu Tachikawa、Akiko Fujii、Matthias Rudolph、A. Stephen K. Hashmi、Hironao Sajiki
DOI:10.1021/acs.orglett.0c00221
日期:2020.3.6
An efficient gold-catalyzed cyclization of 2-alkynylaldehyde cyclic acetals has been developed for the synthesis of indenone derivatives. A wide variety of functionalized indenone derivatives can be obtained in good-to-excellent yields. HMBC and NOESY NMR analyses and mechanistic elucidation experiments revealed that the cyclization occurs via a 1,5-H shift. The cyclic acetal group promoted the 1,5-H
Bromotrimethylsilane (TMSBr)-promoted intramolecular cyclization of (o-arylethynyl)benzylethers to form 1H-isochromenes at room temperature is reported. Further studies indicated that vinyl carbocations are the reaction intermediates which are stabilized by the conjugated aryl groups. Thus, O-addition of benzylethers/tetrahydropyrans to alkynes was achieved under metal-free, acidic conditions. These
报道了溴代三甲基硅烷 (TMSBr) 促进的 ( o -arylethynyl) 苄基醚在室温下分子内环化形成 1 H-异色烯。进一步的研究表明,乙烯基碳阳离子是由共轭芳基稳定的反应中间体。因此,在无金属、酸性条件下实现了苄基醚/四氢吡喃与炔烃的O-加成。这些反应条件与炔基普林斯反应相容;因此,使用一锅法直接由炔基苯甲醛和炔醇生产1 H-异色烯。