Synthetic Applications of Stereodefined 2-Substituted 1-Silyl-1-stannylethenes: A New Synthesis of 5-Ethenyl-5′-(1-propynyl)-2,2′-bithiophene, a Naturally-Occurring Phototoxin)
作者:Renzo Rossi、Adriano Carpita、Tommaso Messeri
DOI:10.1080/00397919108021778
日期:1991.9
(E)-2-(5-Trimethylstannyl-2-thienyl)ethenyldimethylphenylsilane, (E)-8, which can be stereospecifically prepared from (Z)-1-dimethylphenylsilyl-2-(2-thienyl)-1-trimethylstannylethene, (Z)-6, or from (E)-2-(2-thienyl)ethenyldimethylphenylsilane, (E)-9, serves as an equivalent to the 2-ethenylthiophene d1', d5-synthon, 20, in an efficient two-step synthesis of 5-ethenyl-5'-(1-propynyl)-2,2'-bithiophene, 10, a naturally-occurring photoxin. In the first step of this synthesis compound (E)-8 undergoes a palladium-catalyzed cross-coupling reaction with 2-iodo-5-(1-propynyl)thiophene, 16, and in the second step the so obtained cross-coupling product, (E)-17, undergoes a protodesilylation reaction.
(E)-2-(5-三甲基-2-硫王基-2-核糖基)乙烯基双甲基苯硅烷(缩写为(E)-8),它可以通过从(Z)-1-双甲基苯基硅基-2-(核糖基)-1-三甲基-2-硫基乙二烯(缩写为(Z)-6)或从(E)-2-(核糖基)乙烯基双甲基苯硅烷(缩写为(E)-9)的特定立体选择性合成,并在高效两步合成中作为2-乙烯基 thiophene 的等效 d1'、d5 合成单元(编号为 20)发挥作用,从而合成天然产的光素 5-乙烯基-5' -(丙炔基)-双 thiophene 二聚体(编号为 10)。在合成第一阶段,这种(E)-8 粉末状物通过 Pd催化的交叉偶联反应与 2-碘-5-(丙炔基) thiophene(编号为 16)反应。步骤二,所得交叉偶联产物(E)-17 通过亲核去基团化反应。