Palladium‐Catalyzed Annulation of 1,2‐Diborylalkenes and ‐Arenes with 1‐Bromo‐2‐[(Z)‐2‐bromoethenyl]arenes: A Modular Approach to Multisubstituted Naphthalenes and Fused Phenanthrenes |
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| Authors: | Prof?Dr Masaki Shimizu Yosuke Tomioka Dr Ikuhiro Nagao Tsugumi Kadowaki Prof?Dr Tamejiro Hiyama |
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| Institution: | 1. Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto University Katsura, Nishikyo‐ku, Kyoto 615‐8510 (Japan), Fax: (+81)?75‐383‐2445 http://www.npc05.kuic.kyoto‐u.ac.jp/npc05/Home.html;2. Current address: Research & Development Initiative, Chuo University, 1‐13‐27, Kasuga, Bunkyo‐ku, Tokyo 112‐8551 (Japan) |
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| Abstract: | (Z)‐1,2‐Diaryl‐1,2‐bis(pinacolatoboryl)ethenes underwent double‐cross‐coupling reactions with 1‐bromo‐2‐(Z)‐2‐bromoethenyl]arenes in the presence of Pd(PPh3)4] as a catalyst and 3 M aqueous Cs2CO3 as a base in THF at 80 °C. The double‐coupling reaction gave multisubstituted naphthalenes in good to high yields. Annulation of 1,2‐bis(pinacolatoboryl)arenes with bromo(bromoethenyl)arenes in the presence of a catalyst system that consisted of Pd2(dba)3] (dba=dibenzylideneacetone) and 2‐dicyclohexylphosphino‐2′,6′‐dimethoxybiphenyl (SPhos) under the same conditions produced fused phenanthrenes in good to high yields. The first annulation coupling occurred regiospecifically at the bromoethenyl moiety. This procedure is applicable to the facile synthesis of polysubstituted anthracenes, benzothiophenes, and dibenzoanthracenes through a double annulation pathway by using the corresponding dibromobis(Z)‐2‐bromoethenyl]benzenes as diboryl coupling partners. |
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| Keywords: | annulation arenes boron cross‐coupling palladium |
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