Visible Light-Mediated Construction Of C-O/C-C Bonding Reaction Catalyzed By Tetrabromomethane

In recent years,visible light-induced catalytic cross-coupling reactions for the construction of carbon hetero（C-X）bonds have become an emerging field in organic chemistry.In a general sense,these methods rely on metal complexes and organic dye photocatalysts to convert visible light into chemical energy by single electron transfer with organic substrates to produce reaction intermediates.Carbon tetrabromide（CBr₄）,as a simple organic small molecule reagent,is a highly promising photocatalyst under certain conditions due to its good stability,easy handling and good reactivity for Cross-Dehydrogenative Coupling（CDC）reactions.Because of these advantages,carbon tetrabromide is often applied in organic transformations,but mediating/catalyzing cross-coupling reactions to construct C-X bonds under visible light conditions is relatively limited.In this paper,carbon-oxygen（C-O）coupling products and carbon-carbon（C-C）coupling products were synthesized under visible light conditions using carbon-tetrabromide mediated/catalyzed cross-coupling reactions,respectively.The specific study consisted of two parts:ketoxime/aldoxime and aryl malononitrile derivatives were coupled with tetrahydrofuran,respectively.Firstly,when 1.8 chemical equivalents of carbon tetrabromide were added to the reaction system of cyclic ethers such as ketoxime/aldoxime and tetrahydrofuran（THF）,the C-O coupled oxime ether product could be obtained by light irradiation reaction for 5 h.It was easy to perform gram-scale reaction and showed high reaction performance under sunlight.Secondly,by adding 0.1 chemical equivalents of carbon tetrabromide to the reaction system of aryl malononitrile derivatives and cyclic ethers such as tetrahydrofuran,the C-C coupling product can be obtained by light irradiation reaction for 36 hours.None of the above reactions involved transition metals,the reaction conditions were mild,the functional groups were well tolerated,and the target products were obtained in good yields.Finally,the possible reaction mechanism was deduced from theoretical calculations,deuteration experiments,ultraviolet-visible spectroscopy and radical trapping.