Transition‐Metal‐Catalyzed Direct Arylation of Caged Silsesquioxanes: Substrate Scope and Mechanistic Study

摘要

>Caged silsesquioxane (polyhedral oligomeric silsesquioxane: POSS) is an important class of organic‐inorganic hybrid molecules. The electronic properties of POSS have gradually attracted attention from experimental and computational perspectives, while POSS is generally utilized for reinforcement of polymer materials. Practical synthetic routes to access to aryl‐substituted POSS are effective tools for the systematic studies. Recently, we reported Rh‐catalyzed direct arylation of heptaisobutyl‐POSS with electron‐rich aryl iodides. Herein substrates for the Rh‐catalyzed direct arylation were widely examined: electron‐deficient, sterically‐hindered, and heteroatom‐containing aryl halides, and heptaphenyl‐POSS. Pd‐catalyzed direct arylation of POSS was developed as well. Notably, thiophene was introduced by the Pd‐catalyst, whereas the Rh‐system did not work for the substrate. In addition, the reaction mechanism of the Rh‐catalyzed reaction was elucidated by density functional theory calculations.