Transition metal catalysis for aerobic C-H oxidation reactions and for the synthesis of fluoranthene derivatives

Abstract

Within the past two decades, a powerful class of new reactions that introduces oxidized functionality to (sp3) C-H bonds has emerged and gained tremendous attention since it can revolutionize the chemical industry by placing reactive functional groups directly in a molecule. Usually, precious metals (e.g., Pd, Pt, Ru etc.) are used for the activation of C-H bonds, and finding alternative ways that use less expensive and less toxic first row transition metals to replace precious metal catalysts is necessary. In this work, we have developed a reductive pretreatment system to increase the activity of precious metal-free LaMnO3 perovskites for C-H oxidation reactions of alkylarenes to ketones or oxidative dimerization of naphthols under mild conditions. Furthermore, a bimetallic nickel-manganese based hydroxide catalyst was synthesized as well and it was proven to oxidize a variety of alkylarenes and alcohols. Using molecular oxygen as the sole oxidant in C-H oxidation reactions is another advantage of our method since it is green, inexpensive and readily available in nature. In the second part, two novel methods have been developed for the synthesis of fluoranthenes which are important polycyclic skeletons. They can be found in many natural products, organic electronics, dyes and various materials. These methods employ Pd-catalyzed cross-coupling reactions such as Suzuki-Miyaura and Sonogashira reactions in the first steps using 1,8-dihalonaphthalenes and then use intramolecular Diels-Alder reactions for the formation of tetracyclic ring in the fluoranthene core. Our methods also provide a modular pathway for the synthesis of multi-substituted fluoranthene derivatives from simple molecules because it is designed as a three-component system and each component can be readily prepared or functionalized allowing easy modification.