1-苯基苯并[ b ]噻吩三氟甲磺酸盐在180℃下的热分解导致苯基迁移,从而以高收率得到2-苯基苯并[ b ]噻吩。有趣的是,在2位具有取代基的1-苯基苯并[ b ]噻吩三氟甲磺酸酯的热解得到相应的3-苯基苯并[ b ]噻吩。基于2-(4-甲基苯基)-1-苯基苯并[ b ]噻吩鎓三氟甲磺酸酯的热解,提出了连续的[1,5]σ重排用于苯基迁移。
Novel [4 + 2]-Cycloaddition of 1-Phenyl-1-benzothiophenium Salts with Dienes. Experimental Evidence for a Lack of Aromaticity in the Thiophene Ring
作者:Tsugio Kitamura、Bian-Xiang Zhang、Yuzo Fujiwara
DOI:10.1021/jo020406p
日期:2003.2.1
The [4 + 2]-cycloaddition reaction of 1-phenyl-1-benzothiophenium triflates has been conducted for the first time. [4 + 2]-Cycloaddition with dienes such as cyclopentadiene and 1,3-diphenylisobenzofuran occurs successfully to give cycloadducts. This result indicates that the C=C bond of the thiophene ring acts as a 2pi electron component in the cycloadditionreaction. Cycloadducts were formed in high
Photolysis of 1-phenylbenzo[b]thiophenium salts was conducted by use of a Pyrex-filtered high-pressure Hg lamp. The major products in most cases were the phenyl-migrated ones, i.e., 2-phenylbenzo[b]thiophenes and 3-phenylbenzo[b]thiophenes, together with the dephenylated benzo[b]thiophenes. This photochemical behavior is quite different from the thermal ones that provide the ring-opened olefins. The
The reaction of 1-phenyl-1-benzothiophenium triflates 1 (R = H, Me, and Ph) with cyclopentadiene successfully proceeded to give the corresponding cycloadducts, respectively, in good yields. The single-crystal X-ray analysis of 1 (R = H) showed the endo isomer. Similarly, 1,3-diphenylisobenzofuran reacted with 1 (R = H) to give the corresponding cycloadduct. These novel [4 + 2] cycloadditions of 1-phenyl-1- benzothiophenium triflates as the first example clearly indicate the olefinic nature of the thiophene ring arising from the lack of aromaticity.