Dipartimento di Scienze Farmaceutiche, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy.
J Org Chem. 2011 Oct 21;76(20):8277-86. doi: 10.1021/jo201471k. Epub 2011 Sep 22.
Novel and convenient approaches to benzothiophene derivatives 3 and 5 have been developed, based on heterocyclization reactions of 1-(2-mercaptophenyl)-2-yn-1-ols 2 or 4, respectively, readily available from alkynylation of 2-mercaptobenzaldehydes or 1-(2-mercaptophenyl) ketones 1. In particular, 1-(2-mercaptophenyl)-2-yn-1-ols 2, bearing a CH(2)R substituent on the triple bond (R = alkyl, aryl), were conveniently converted in fair to good yields (55-82%) into (E)-2-(1-alkenyl)benzothiophenes 3 when allowed to react in the presence of catalytic amounts (2 mol %) of PdI(2) in conjunction with KI (KI:PdI(2) molar ratio =10) at 80-100 °C in MeCN as the solvent, through a heterocyclodehydration process. On the other hand, 2-alkoxymethylbenzothiophenes 5 were selectively obtained in fair to excellent yields (49-98%) via a radical-promoted substitutive heterocyclodehydration process, by reacting 1-(2-mercaptophenyl)-2-yn-1-ols 4 (bearing an alkyl or aryl substituent on the triple bond) in alcoholic media at 80-100 °C in the presence of a radical initiator, such as AIBN.
已经开发出了一种新颖而方便的苯并噻吩衍生物 3 和 5 的方法，该方法基于 1-(2-巯基苯基)-2-炔-1-醇 2 或 4 的杂环化反应，这两种化合物分别可以从 2-巯基苯甲醛或 1-(2-巯基苯基)酮 1 的炔基化反应中很容易获得。特别是，1-(2-巯基苯基)-2-炔-1-醇 2 在三键上带有 CH(2)R 取代基（R = 烷基，芳基），当在存在催化量（2 mol%）的 PdI(2)和 KI（KI:PdI(2)摩尔比=10）的情况下，在 80-100°C 下在 MeCN 中作为溶剂反应时，通过杂环脱水过程，以中等至良好的收率（55-82%）转化为（E）-2-（1-烯基）苯并噻吩 3。另一方面，通过在 80-100°C 下在醇性介质中，在自由基引发剂（例如 AIBN）的存在下，使 1-(2-巯基苯基)-2-炔-1-醇 4（在三键上带有烷基或芳基取代基）反应，可以选择性地以中等至优异的收率（49-98%）得到 2-烷氧基甲基苯并噻吩 5，该反应通过自由基促进的取代杂环脱水过程进行。
