Department of Applied Chemistry, Okayama University of Science, Okayama 700-0005, Japan.
Org Lett. 2012 Aug 3;14(15):3970-3. doi: 10.1021/ol3017353. Epub 2012 Jul 16.
Diiodo- and bromo, iodo-substituted dibenzopentalenes were obtained by treatment of 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctene with I(2) and IBr, respectively. These dihalo-substituted pentalenes reacted with terminal ethynes in Sonogashira coupling and with arylboronic acid in Suzuki-Miyaura coupling to give a series of phenylethynyl- and/or aryl-substituted pentalenes. Suzuki-Miyaura coupling of the halopentalenes with in situ prepared pentaleneboronic esters provided bis-, tri-, and tetra(dibenzopentalene)s. It was found that these dibenzopentalene oligomers underwent facile electrochemical reduction and exhibited a bathochromic shift in UV-vis absorption spectra because of their expanded π-systems.
二碘代和溴代、碘代取代的二苯并戊二烯通过用 I(2)和 IBr 分别处理 5,6,11,12-四去氢二苯并[a,e]环辛烯而获得。这些卤代取代的戊二烯与末端炔烃在 Sonogashira 偶联反应中以及与芳基硼酸在 Suzuki-Miyaura 偶联反应中反应，得到一系列苯乙炔基和/或芳基取代的戊二烯。卤代戊二烯与原位制备的戊二烯硼酸酯的 Suzuki-Miyaura 偶联提供了双、三、四（二苯并戊二烯）。发现这些二苯并戊二烯齐聚物易于进行电化学还原，并由于其扩展的π体系而在 UV-vis 吸收光谱中表现出红移。
