第9族金属触媒を用いる1,6-ジイン誘導体の環化異性化反応による多彩な環骨格構築法の開発

抄録

Polycyclic structures are found in many natural products and pharmaceuticals. The transition-metal-catalyzed cycloisomerization of unsaturated compounds is one of the most powerful methods for construction of polycyclic frameworks in a single operation. In particular, 1,6-diyne is the structural motif widely used for the cycloisomerization as it readily reacts with low-valent metal catalysts to form metallacyclopentadiene intermediates. However, this method has been mainly exploited for the synthesis of aromatic compounds such as benzenes and pyridines. This article describes our recent studies regarding the synthesis of various polycyclic structures including non-aromatic carbocycles, such as 5-6-5 tricyclic cyclohexadienes bearing a quaternary bridgehead carbon and tetralone-containing exocyclic dienes, via the group 9 metal-catalyzed cycloisomerization reaction of 1,6-diyne derivatives. In the course of our study, we elucidated that the cobalt/photoredox dual catalysis is very efficient for the cycloisomerization of 1,6-diyne derivatives such as enediynes. We also found a novel cascade cyclization of 1,6-diynyl esters to form various cyclic compounds through the formation of vinylallene intermediates.