Studies On Visible Light Induced Cross-Dehydrogenative Coupling Reaction: The Synthesis Of α-Aryl Glycine Derivative And 1,3-Benzoxazines

The cross dehydrogenative coupling（CDC）reaction has emerged as one of the most straightforward and atom-economical approaches for constructing C?C bonds,as it avoids the tedious prefunctionalization of the starting materials.Visible light-induced photoredox catalysis has recently become a powerful protocol to trigger the CDC reaction,owing to its mild,clean,and environmentally benign characteristics.This thesis mainly studies the oxidative cross-dehydrogenative coupling reaction of glycine derivatives with electron-rich arenes via the synergistic combination of photoredox catalysis and Lewis acid catalysis.The main work could be divided into the following two parts:1.We have developed a direct aerobic oxidative dehydrogenative coupling reaction of glycine derivatives with electronrich arenes.In the presence of Rhodamine6G and FeSO₄·7H₂O,a large number of arylglycine derivatives were successfully synthesized with 41-86%yield under the irradiation of 3 W blue LED at room temperature.Compare to previous reported strategy,the major innovation of current work is using a cheap and environmental friendly organic dye as the photocatalyst,thereby avoiding expensive transition metal catalysts,which means more greener and cost-effective.At the same time,given the diverse range of organic substrates,and the mild and operationally simple reaction conditions,this visible-light-induced C-H functionalization protocol should find broad application in the synthesis of glycine derivatives.2.The 1,3-benzoxazine skeletons are privileged structural units that exist widely in pharmaceutically active molecules,which also serve as important synthetic intermediates for the synthesis of bioactive natural products.Inspired by our previous work,we hypothesized that whether arylglycines could trap another equivalent of imine intermediate,thereby providing a new strategy for the synthesis of1,3-benzoxazines.Finally,we obtained a series of 1,3-benzoxazine derivatives in65-84%yield at room temperature using Ru（bpy）₃Cl₂·6H₂O as photocatalyst and Cu（OTf）₂ as co-catalyst under the irradiation of 3W blue LED.Electron-rich aromatic glycine derivatives and imines were proved to be the important intermediates in the reaction.The potential synthetic value of this novel protocol was exemplified by a gram-scale reaction.