2,2'-雙(苯乙炔基)-4,4'-雙取代聯苯關環反應機制的研究

Abstract

2,2’-雙(苯乙烯基)-聯苯，在高溫下會進行分子內的關環反應，得到化合物6。為了確認反應機制是經由何種中間體，我們合成了一系列的2,2’-雙(苯乙烯基)-4,4’-雙取代聯苯，嘗試以四苯基環戊二烯酮，捕捉benzocyclobutadiene類型的反應中間體。我們成功地得到此中間體與四苯基環戊二烯酮進行加成反應的產物化合物7。因此我們認為反應是經由benzocyclobutadiene類型的中間體，而非diradical類型的中間體。但也無法完全排除經由diradical 途徑的可能性。另外，我們也探討4,4’位置上不同官能基，對於此反應的影響。

2,2'-di(phenylethynyl)-biphenyls undergo thermal cyclization reaction at high temperature (260℃) to yield compound 6. To probe the reaction mechanism, a series of 2,2'-di (phenylethynyl)-4,4'-disubstitued-biphenyl were synthesized and then were subjected to the reeaction conditions . In order to differentiate the diradical or benzocyclobutadiene mechanism, we added tetraphenylcyclo- pentadienone to trap the intermediate. Cyclooctatetraene derivatives, which were derived from addition reaction of tetraphenylcyclopentadienone and benzocyclobutadiene intermediate, were finally isolated. As a result, we concluded that the cyclization proceeds through the benzocyclobutadiene process. However the possibility of the diradical pathway couldn’t be completely excluded. We also explored the effects of the 4,4’-disubstitued functional groups on the thermal cyclization reaction.