Pyridine-substituted hydroxythiophenes. IV. Preparation of 3- and 4-(2-, 3- and 4-pyridyl)-2-hydroxythiophenes
作者:Yihua Zhang、Anna-Britta Hörnfeldt、Salo Gronowitz
DOI:10.1002/jhet.5570320209
日期:1995.3
boron tribromide to give 3-(3-pyridyl)-3-thiolene-2-one, which only was stable in ether solution at −20°. The attempted demethylation of 2-methoxy-3-(2-pyridyl)thiophene with trimethylsilane chloride/sodium iodide in refluxing acetonitrile led to a dimer. Demethylation of the 2-methoxy-3-pyridylthiophenes with dibenzyl diselenide and sodium borohydride gave 3-pyridylthiophan-2-ones.
通过三个异构体溴吡啶与3-三甲基锡烷基-2-甲氧基噻吩的Pd(0)-催化偶合,已经以高收率制备了3-(2-,3-和4-吡啶基)-2-甲氧基噻吩。该化合物是通过3-溴-2-甲氧基噻吩的卤素-金属交换,然后进行甲锡烷基化反应制得的。通过2-甲氧基噻吩的二溴化和α-脱溴制备3-溴-2-甲氧基噻吩。使用各种试剂对2-甲氧基-3-吡啶基噻吩进行脱甲基的大多数尝试均失败了,这可能是由于所需的3-吡啶基-2-羟基噻吩系统的不稳定性和高反应活性。只有2-甲氧基-3-(3-吡啶基)噻吩与三溴化硼反应生成3-(3-吡啶基)-3-噻吩-2-酮,其仅在-20℃的醚溶液中稳定。在回流的乙腈中尝试用三甲基硅烷氯化物/碘化钠使2-甲氧基-3-(2-吡啶基)噻吩脱甲基化导致了二聚体。用二苄基二硒化物和硼氢化钠对2-甲氧基-3-吡啶基噻吩进行脱甲基,得到3-吡啶基噻吩-2-酮。