From β-Nitrothiophenes to Ring-Fused Nitrobenzenes: An Overall Ring-Enlargement Process via a Facile, Aromatization-Driven, Thermal 6π Electrocyclization<sup>1</sup>
作者:Lara Bianchi、Carlo Dell'Erba、Massimo Maccagno、Giovanni Petrillo、Egon Rizzato、Fernando Sancassan、Elda Severi、Cinzia Tavani
DOI:10.1021/jo051059x
日期:2005.10.1
the 3-unsubstituted derivatives 8, deriving from the initial ring opening of 3-nitrothiophene (2), have been likewise found herein to undergo cyclization, followed by aromatization, in analogous mild experimental conditions, leading to the ring-fused homo- or heteroaromatic nitro derivatives 10. The concerted electrocyclic nature of the process is strongly supported by the outcome of tests based on
在对先前关于1-芳基-4-甲磺酰基-2-硝基-3-苯基磺酰基-1,3-丁二烯的热环化的研究中(7),由3的初始开环衍生而来的3-未取代的衍生物8 -硝基噻吩(2),在本文中同样被发现在类似温和的实验条件下进行环化,然后进行芳构化,导致环稠合的均-或杂芳族硝基衍生物10。基于溶剂极性或8芳基上电子密度变化的测试结果强烈支持了该方法的协调一致的电环性质。因此,该方法成功地应用于非苯磺酰基活化的图8显着拓宽了由硝基噻吩合成的有价值的总的开环/闭环方法的范围。此外,提供了对最近对热6π电环化的新兴趣的支持,所述热6π电环化是用于构建苯环的工具。