New Reaction Development with Organometallic Catalyst: Part I. Amide Synthesis Using Catalytic Alcohol Activation Strategy Part II. Visible Light Photoredox Catalyst Mediated C(sp3)−H Functionalization

Abstract

The research described in this thesis covers development of new organic reactions catalyzed by organometallic complexes. The thesis is divided into two parts according to the catalytic strategy used. Part I introduces a new catalytic amide synthetic method utilizing dehydrogenative alcohol activation strategy. It is atom-economical and environmentally benign alternative of classical amide synthetic strategies. The basic concept of the strategy and state-of-the-art examples are discussed in Chapter 1. 100% atom economical amide synthesis using alcohols and nitriles as reactant is achieved with N-heterocyclic carbene (NHC) coordinated ruthenium catalyst (Chapter 2). NHC-dihydridoruthenium complex is proposed as the active catalytic species, and the involvement of unusual imine intermediate is suggested based on the mechanistic studies. Methanol is a promising C1 building block due to its low toxicity, low cost, and worldwide stabilized production. With well-defined NHC-dihydridoruthenium catalyst, N-formamide is synthesized from either nitrile or amine utilizing methanol as a formylating source (Chapter 3). No extra base or hydrogen acceptor is required.<br/> Part II describes C(sp3)−H activation reactions mediated by visible light photoredox catalysis. C(sp3)−H functionalization is an ideal process in organic chemistry. Recent advance in visible light photoredox catalysis enables selective and efficient C(sp3)−H activation reactions. The concept of the strategy and representative examples are summarized in Chapter 4. Thioesters are versatile synthetic building blocks of complex molecule synthesis and peptide synthesis. The photoredox mediated nickel catalyzed ethereal C(sp3)−H thiocarbonylation reaction is reported (Chapter 5). It is not only the first C(sp3)–H thiocarbonylation reaction, but also the first example of utilizing simple aryl thioester as a thiocarbonylation source instead of CO gas and thiol. Photocatalytic single electron reduction and fragmentation of the thioester is proposed as the key mechanism of the reaction.<br/>