Photoinduced metal-free diboration of alkynes in the presence of organophosphine catalysts
| Autor: | Kei Mihara, Akiya Ogawa, Tomokazu Saeki, Akihiro Nomoto, Yuki Takamachi, Li-Biao Han, Aya Yoshimura, Shinichi Kawaguchi |
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| Rok vydání: | 2016 |
| Předmět: |
010405 organic chemistry
Chemistry Organic Chemistry 010402 general chemistry Photochemistry 01 natural sciences Biochemistry 0104 chemical sciences Catalysis law.invention chemistry.chemical_compound law Drug Discovery Stereoselectivity Octene Selectivity Electron paramagnetic resonance Isomerization Phosphine Vicinal |
| Zdroj: | Tetrahedron. 72:7832-7838 |
| ISSN: | 0040-4020 |
| Popis: | In sharp contrast to the transition metal-catalyzed diboration of alkynes with diboron species such as B 2 pin 2 , which affords vicinal cis -diborated alkenes, the organophosphine-catalyzed addition of B 2 pin 2 to alkynes proceeds under metal-free conditions upon photoirradiation to give the corresponding vicinal trans -diborated alkenes with good stereoselectivity. For example, the photoinduced diboration of 1-octyne with B 2 pin 2 in the presence of tris( o -methylphenyl)phosphine afforded 1,2-diborated octene with excellent trans selectivity ( trans / cis =95/5). The influence of various organophosphines on the diboration is described in detail. The diboration does not occur in the dark or in the absence of an organophosphine catalyst. Moreover, ESR (electron spin resonance) measurements of the reaction mixture revealed a radical species around g =2.003, supporting a radical pathway for the organophosphine-catalyzed diboration. In addition, the photoinduced cis to trans isomerization of vicinal cis -diborated alkenes in the presence/absence of organophosphines is discussed. |
| Databáze: | OpenAIRE |
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