Intermolecular [2+2] Cycloadditions Of Coumarin Derivatives And Polymerization Of Methly Methacrylates By Visible Light

Visible light is abundant in the solar spectrum on the surface of the earth. It is inexpensive, nonpolluting and endlessly renewable source of clean energy. Up to now, visible-light photoredox catalysis has become hot topics of many research fields. This thesis summarized recent development and application of visible light photoredox catalysis in organic synthesis and the importance of visible-light photocatalysis was further strengthened. they were studied that intermolecular [2+2] cycloadditions between coumarin-3- carboxylates and electron-deficient alkenes and control of a living radical polymerization of methyl methacrylates by visible light. The main research content is as follows: 1. At room temperature, Using the Bis[2-(4,6-diflurophenyl)pyridinato-C2,N](picolinato)iridium(Ⅲ)(FIrPic) as a photosensitizer and a 3W blue LED as a light source, an array of clobuta-benzocypyranones were prepared in excellent to moderate yields. The present visible-light driven intermolecular [2+2]cycloadditions are acheived without the help of other additives except for a catalytic amount of FIrPic. The resulting benzocyclobutapyranones can be employed as key building blocks upon ring opening for the generation of tetrahydrodibenzofurans, which are often found in molecules that exhibit biological activities. So the synthetic strategy has potential application value. We found that visible-light driven intermolecular [2+2] cycloadditions using an energy transfer process through a study of reaction mechanism.This is one of the example of few energy-tranfer reactions in the visible li ght catalyzed field. Because the visible-light driven reactions via energy transfer are no longer constrained by the electrochemical properties of the substrates, the present findings are expected to offer an alternative approach to visible light photocatalysis which are unlikely to occur via electron transfer. 2. We have developed a controlled living radical polymerization by visible light. At room temperature, Using the a-bromocarbonyl compounds as initiators and the fac-Ir(ppy)3 as a photosensitizer, Polymethyl methacrylate were prepared. The effects of the amount of catalyst, initiator-to-monomer ratio and on the polymerization of methyl methacrylate were investigated. Through the experiment,we confirmed that the polymerization reaction does not exist the chain transfer reaction and it is a kind of living radical polymerization. The reaction provides a new strategy for the design and synthesis of polymer.