Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion-Activated Alkenes

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• 作者：Hidekazu Arii ; Yuto Yano ; Kenichi Nakabayashi ; Syuhei Yamaguchi ; Masaki Yamamura ; Kunio Mochida ; Takayuki Kawashima
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：August 5, 2016
• 年：2016
• 卷：81
• 期：15
• 页码：6314-6319
• 全文大小：313K
• 年卷期：0
• ISSN：1520-6904

文摘

Treatment of dialkylbenzylsilanes (1) with trityl tetrakis(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium ions in equilibrium with their intra- or intermolecular π-complexes, which underwent dehydrogenative annulation with various alkenes to form 1,2,3,4-tetrahydro-2-silanaphthalenes (4) in up to 82% isolated yield. Sterically bulkier substituents on the silicon atom tended to increase the yield of cyclic products 4. The annulation products retained the stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance of the naphthyl group prevented addition of the cis-alkene to the silylium ion, which would considerably decrease yields of the desired products from 2 compared to those from 1.