Studies On The Cyclization And Oxidation Reactions Based On Azomethine Imines

Azomethine imines are important nitrogen-containing compounds. Their cyclization reactions, oxidation reactions etc are important in organic synthesis. This thesis focuses on developing new types of reactions based on azomethine imines. Novel cyclization and oxidation reactions have been developed for the efficient synthesis of imides, poly-substituted cyclohepta[b]pyrroles, and 1-pyrrolines. These reactions have advantages, such as readily available starting materials, mild reaction conditions, diversity of products, and simplicity of operations. Mechanisms of these reactions are also investigated in details.The thesis is divided into five chapters. In chapter one, the structure, properties,classification, synthetic methods of azomethine imines, and recent development of cyclization and oxidation reactions based on azomethine imines are sumerized. The thesis proposal is presented in chapter two.Chapter three describes an efficient ‘one-pot’ synthesis of imides using molecular oxygen as the oxidant, under extremely mild reaction conditions in the absence of transition metal catalysts and pro-oxidants. It was found that for the first time,α-(alkylideneamino)nitriles can sever as the alkamido(oxo)methanide equivalent(imide building block). Their reactions with electrophiles enabled the straightforward synthesis of imides in good to excellent yields.Chapter four shows a new tandem sequence involving Michael addition/imine isomerization/intramolecular [3+2] cyclization from azomethine imines and α,α-dialkenoyl ketene dithioacetals. The efficient and regiospecific synthesis of cyclohepta[b]pyrrole derivatives could be achieved in a single operation under extremely mild,transition-metal-free conditions starting from readily available acyclic precursors with a broad substrate scope.In chapter five, different from the classical [3+2] cycloaddition reaction of azomethine imines, a wide range of 1-pyrrolines was synthesized from readily available azomethine imines and enones under very mild conditions. This new strategy allows the conversion of Michael adducts to 1-pyrrolines during the separation process on silica gel column chromatography. It has advantages of simple operations, high yields etc and has enriched the cyclization reaction based on azomethine imines.