Design of Reversible Low Redox Potential Systems Using Five-Membered Trichalcogenaheterocycles Containing Heavy Chalcogens; Sulfur, Selenium, and Tellurium
作者:Noriyoshi Nagahora、Satoshi Ogawa、Satoko Yoshimura、Yasushi Kawai、Ryu Sato
DOI:10.1246/bcsj.76.1043
日期:2003.5
4-Isopropyl-7-methoxy-1,3,2-benzodichalcogenastannoles and 2,2-bis(η5-pentamethylcyclopentadienyl)-1,3,2-benzodichalcogenatitanoles, a synthetic equivalent of unstable ortho-benzenedichalcogenol, were prepared from 2-isopropyl-5-methoxybenzenechalcogenols in moderate yields by ortho-lithiation, chalcogenation, and protection with dichlorodimethylstannane and bis(η5-pentamethylcyclopentadienyl)titanocene dichloride, respectively. Some of the solid-state structures of the new-type stannoles and titannoles were confirmed by X-ray crystallographic analyses. Transformation into 4-isopropyl-7-methoxy-1,2,3-benzotrichalcogenoles was successfully carried out, namely by reacting the stannoles or titannoles with electrophiles containing one sulfur or selenium unit. The molecular structures of the new trichalcogenoles were determined by NMR, IR, mass spectra, X-ray crystallographic analyses, and theoretical calculations. In particular, it was elucidated that heavier multi-chalcogen linkages, selenium-selenium and selenium–tellurium bonds in the benzotrichalcogenoles were present in the five-membered ring by multi-nuclear NMR spectra in solution and confirmed by X-ray crystallographic analyses in the solid-state. The redox properties of the trichalcogenoles were studied by cyclic voltammetry. The voltammograms exhibited well-defined reversible one-electron redox couples. New type radical cations were isolated in quantitative yields in the one-electron oxidation of the trichalcogenoles with equimolar amounts of NOPF6. The structures of the radical cation salts were analyzed by 31P-NMR, ESR spectra, elemental analyses, and theoretical calculations. One-electron reduction of the radical cations on treatment with one equivalent of samarium(II) iodide gave the neutral trichalcogenoles quantitatively.
4-异丙基-7-甲氧基-1,3,2-苯并二羰基甾烯和 2,2-双(η5-五甲基环戊二烯基)-1,3,2-苯并二羰基檀烯,一种不稳定的邻苯二羰基烯醇的合成等价物、通过正硫化、羰基化以及二氯二甲基锡和双(η5-五甲基环戊二烯基)二氯二茂钛的保护,分别以中等产率从 2-异丙基-5-甲氧基苯并二羰基烷醇制备了这些化合物。X 射线晶体分析证实了新型锡烯和钛烯的部分固态结构。通过使锡烯和噻吩与含有一个硫或硒单元的亲电体反应,成功地转化成了 4-异丙基-7-甲氧基-1,2,3-苯并三氢羰基烯醇。通过核磁共振、红外光谱、质谱、X 射线晶体分析和理论计算,确定了新的三钙烯醇的分子结构。特别是,通过溶液中的多核核磁共振谱分析,阐明了苯并三钙烯醇中较重的多钙烯醇连接、硒-硒键和硒-碲键存在于五元环中,并通过固态的 X 射线晶体分析得到了证实。通过循环伏安法研究了三钙烯醇的氧化还原特性。伏安图显示了定义明确的可逆单电子氧化还原偶。在三钙苷元与等摩尔量的 NOPF6 进行单电子氧化反应时,可以定量分离出新型自由基阳离子。通过 31P-NMR、ESR 光谱、元素分析和理论计算分析了自由基阳离子盐的结构。用一个当量的碘化钐(II)对自由基阳离子进行单电子还原,定量得到了中性三钙烯醇。