Study On Proton Acid Catalyzed [4+2] Cycloadditon Of Ohydroxybenzyl Alcohol And Heteroatom Alkynes To Synthesize Oxygen-Containing Heterocycies

In the cycloaddition reaction,the [4 + 2] cycloaddition reaction is often used to construct a six-membered ring.This article focuses on the [4+ 2] cycloaddition reaction of o-hydroxybenzyl alcohol and heteroatom alkynes with proton acid as a catalyst.In this article,the [4 + 2]cycloaddition reaction of o-hydroxybenzyl alcohol and heteroatom alkynes has successfully synthesized two different oxygen-containing sixmembered heterocycles.The article is mainly divided into the following three parts:(1)Briefly state the research progress of oxygen-containing heterocyclic 2H-chromene and dihydrocoumarin.(2)The synthesis of 2Hchromene by the [4 + 2] cycloaddition of o-hydroxybenzyl alcohol and alkyne sulfide under the catalysis of protic acid was studied.The reaction conditions are mild,the atom economy is good,and an unexpected [4 + 2]cycloaddition reaction is used to synthesize polysubstituted 2H-chromene with synthetic value.(3)In the presence of traceless sulfonamide guiding groups,proton acid catalyzed the [4 + 2] cycloaddition reaction of ohydroxybenzyl alcohol and alkynamide to synthesize trans 3,4-diaryl dihydrocoumarin.The reaction is green and efficient,the substrate range is wide,and the thermodynamically stable trans 3,4-diaryl dihydrocoumarin is obtained with excellent regioselectivity and good yield.