AMVN-initiated expedient synthesis of biaryls by the coupling reaction of unactivated arenes and heteroarenes with aryl iodides
作者:Bhagat Singh Bhakuni、Abhimanyu Yadav、Shailesh Kumar、Sangit Kumar
DOI:10.1039/c3nj01105d
日期:——
The role of radical initiators AMVN and AIBN has been studied in the potassium tert-butoxide mediated biaryl coupling reaction of aryl iodides with unactivated arenes. Radical initiator AMVN promoted carbon–carbon bond formation expeditiously from aryl iodide having various groups such as amino, methoxy, fluoro, methyl, and trifluoromethyl and arenes in the presence of potassium tert-butoxide (4 equiv.) at 110 °C in 2–5 h. Substituted arenes such as toluene, xylene, anisole, and fluorobenzene also proceeded to form biaryls under AMVN-initiated reaction conditions. Moreover naphthalene, pyridine, pyrimidine, and pyridazine also coupled with aryl iodides and produced biaryls in 41–82% yields. It seems that AMVN initiates the formation of the aryl radical, which enters the radical chain reaction. The generated aryl radical may combine with the arene leading to a biaryl radical, which upon protonation gives the biphenyl radical anion and tert-butanol. The biphenyl radical anion finally reacts with the aryl iodide generating the aryl radical and thus completes the radical chain reaction with concomitant release of biphenyl.
自由基引发剂AMVN和AIBN在钾叔丁醇介导的芳基碘与未活化芳烃的双芳基偶联反应中的作用已被研究。自由基引发剂AMVN促进了不同取代基(如氨基、甲氧基、氟、甲基和三氟甲基)芳基碘与芳烃的碳–碳键形成,在钾叔丁醇(4当量)存在下,于110°C反应2–5小时。取代芳烃如甲苯、二甲苯、乙酸苄酯和氟苯在AMVN引发的反应条件下也能够形成双芳基。此外,萘、吡啶、嘧啶和吡嗪也与芳基碘偶联,产率为41–82%。看来AMVN能够引发芳基自由基的形成,并进入自由基链反应。生成的芳基自由基可能与芳烃结合形成双芳基自由基,随后经过质子化形成联苯自由基阴离子和叔丁醇。联苯自由基阴离子最终与芳基碘反应生成芳基自由基,从而完成自由基链反应,并伴随释放联苯。