鈀金屬催化環化反應合成雙取代基亞甲基烯茀與苯并[a]咔唑化合物

Abstract

Abstract In chapter two, the palladium-catalyzed annulation reaction of 2-(1-alkynyl)biphenyls with aryl iodides to give diarylmethylidenefluorenes is described. Specifically the pertinent synthesis involves 2-(1-alkynyl)biphenyls with 3 equivalents of aryl iodides in DMF/ H2O (10/1) in the presence of 5 mol % of Pd(OAc)2 and 2 equivalents of K2CO3 at 110oC. This method tolerates various functional groups in aryl iodide, such as OCH3, CH3, Cl, Br, CF3 and NO2. All proceed in good yield with the exception of 4-iodonitrobenzene. In chapter three, the palladium-catalyzed cyclization of enediynes to benzo[a]carbazoles is described. Treatment of N,N-dimethyl 2-[2-(2-ethynylphenyl)ethynyl]anilines with 10 mol% of palladium dichloride and 2 equivalents of cupric chloride in refluxing THF gave benzo[a]carbazoles in good yields. A mechanistic study showed that this reaction must proceed through formation of haloindole followed by a palladium(II)-catalyzed atom transfer cyclization reaction to give the benzo[a]carbazoles. In chapter four, we found iodine can also catalyzed the cyclization of haloindoles to give benzo[a]carbazoles. Treatment of N,N-dimethyl 2-[2-(2-ethynylphenyl)ethynyl]anilines with 1.2 equivalents of iodine in CH2Cl2 at room temperature gave benzo[a]carbazoles in good yields. In some cases, while the substrates bearing t-butyl at the terminal alkyne or electron withdrawing group at the amine, the reaction stop at the haloindoles rather than benzo[a]carbazoles.