2,3,4-三甲氧基苯基-苯基-烯酮与乙氧基乙炔的加成重排反应

研究了2,3,4-三甲氧基苯基-苯基-烯酮(9)与乙氧基乙炔的加成-重排反应, 得到2种薁酮异构体产物(11和12), 其结构经核磁共振波谱和X射线单晶衍射分析进行了确证. 该研究结果为Woodward所提出的分步反应机理提供了实验依据.

Reaction of 2-Phenyl-2-(2,3,4-trimethoxyphenyl)ketene with Ethoxyethyne†

Nieuwenhuis and Arens discovered the reaction of diarylketenes with alkynyl ethers leads to substituted azulenones in 1958. This reaction involved the construction of four C—C bonds in a single operation and provided facile access to a functionalized bicyclo[5.3.0]decane skeleton. Although the mechanism of this transformation was rationalized later by Woodward and Barton, respectively, the synthetic value of this reaction has not been demonstrated so far. In this work, 2-phenyl-2-(2,3,4-trimethoxyphenyl)ketene(9) as a new ketene was first synthesized from 1,2,3-trimethoxybenzene and ethyl 2-chloro-2-oxoacetate through 5 steps. The reaction of compound 9 with ethoxyethyne(2) produced two novel angular aryl-substituted azulenone products 11 and 12, whose isomeric structures were characterized by NMR and X-ray crystallographic analysis. Treatment of azulenone 11 with Lewis acid afforded azulenone 12. These results provided an additional experimental supported for a stepwise pathway rationalized by Woodward earlier on.