Synthesis of new methylated thieno[2,3-<i>a</i>] and [3,2-<i>b</i>]carbazoles by reductive cyclization of 6-(2′-Nitrophenyl)benzo[<i>b</i>]thiophenes obtained by palladium-catalyzed cross-coupling isabel
作者:C. F. R. Ferreira、Maria-João R. P. Queiroz、Gilbert Kirsch
DOI:10.1002/jhet.5570380334
日期:2001.5
[3,2-b]carbazoles (5) (R=H) was achieved by a palladium-catalyzed cross-coupling, intramolecular reductive cyclization sequence of reactions. The cyclization precursors 6-(2′-nitrophenyl)benzo[b]thiophenes (3) were obtained by Suzuki cross-coupling of 6-boronated methylbenzo[b]thiophenes intermediates (2) with 2-bromo or iodonitrobenzene. The boronated intermediates (2) were prepared via bromine-lithium
新的甲基化噻吩并[2,3-a]和[3,2-b]咔唑(5)(R = H)的合成是通过钯催化的交叉偶联,分子内还原环化反应来实现的。通过将6-硼代甲基苯并[ b ]噻吩中间体(2)与2-溴或碘硝基苯进行Suzuki交叉偶联,得到环化前体6-((2'-硝基苯基)苯并[b]噻吩(3)。硼化中间体(2)的制备是通过溴-锂交换,然后进行硼金属转移,并使用Pd(OAc)2原位偶联,从而从6-溴苯并[ b ]硫代苯( 1)到环化前体(3)。在还原环化步骤中,还获得了N-乙基噻吩并咔唑(5)(R = Et)。为了避免形成亚磷酸三乙酯的量和反应时间,已经进行了一些实验。