Synthesis of polycyclic and 4,5-diacylthiophene-2-carboxylates via intramolecular Friedel–Crafts alkylations and unusual autooxidative fragmentation of the derivatives obtained from the samarium diiodide-promoted coupling reactions of thiophene-2-carboxylate with carbonyl compounds
作者:Shyh-Ming Yang、Jim-Min Fang
DOI:10.1016/j.tet.2006.11.080
日期:2007.2
Our present study provides an expedient method for the synthesis of novel polycyclic and multi-substituted thiophene derivatives. A series of 4,5-di(hydroxyalkyl)-4,5-dihydrothiophene-2-carboxylates (e.g., 4a–c and 10) were prepared by the SmI2-promoted three-component coupling reactions of thiophene-2-carboxylate with aromatic aldehydes and 4-methoxyacetophenone. Diol 4a was oxidized by DDQ or pyridinium
我们目前的研究为合成新型多环和多取代噻吩衍生物提供了一种简便的方法。通过SmI 2促进的噻吩2-羧酸三组分的三组分偶联反应,制备了一系列的4,5-二(羟烷基)-4,5-二氢噻吩2-羧酸盐(如4a - c和10)。芳香醛和4-甲氧基苯乙酮。将二元醇4a用DDQ或重铬酸吡啶鎓氧化,得到5-酰基-4-羟烷基-4,5-二氢噻吩-2-羧酸酯6a,然后对其进行脱水,得到带有末端CC双键的烯烃7或烯烃15a。取决于使用不同量的对甲苯磺酸的反应条件,其与酯基共轭。烯烃7经历分子内Friedel-Crafts烷基化反应,得到四氢萘酮稠合的噻吩-2-羧酸酯9。通过类似的步骤,还制备了咔唑稠合的噻吩14。烯烃15a – c经过自氧化裂解,得到4,5-二酰基噻吩-2-羧酸盐5a – c,这些化合物被制成哒嗪融合的噻吩。