Synthesis Of γ-Lactones Catalyzed By Re₂O₇ And Asymmetric Synthesis Of Benzopyran Derivatives Catalyzed By Chiral Phosphoric Acid

Oxygen-containing heterocyclic compounds,especially the five-memberedγ-lactone and the six-membered benzopyran,have wide applications in biology,medicinal chemistry,material science,etc.After investigation,we find that the synergistic effect of Re₂O₇and HFIP is beneficial to the formation of highly electron-deficient unstable carbocations,thereby catalyzing the intramolecular hydroacyloxylation of inert olefins to synthesizeγ-lactones.In addition,in recent years,most of the research on the synthesis of benzopyrans have focused on diastereoselective synthesis,while the research on enantioselective synthesis is relatively rare.The study found that the enantioselective synthesis of benzopyran catalyzed by chiral phosphoric acid is a new method with environmentally friendly,economical steps,low cost and simple operation.Based on this,the main research contents of this article are as follows:（1）In the first part,this article uses the co-action of Re₂O₇and HFIP to catalyze the intramolecular hydroacyloxylation of inert olefins with electron-withdrawing groups,and successfully synthesizesγ-lactone.The main advantages of this reaction are no need for co-catalysis,low catalyst loading,mild reaction conditions,atom economy,and high yield.In addition,this article also investigated the effects of catalyst types,catalyst equivalents,solvent types and other factors on the synthesis ofγ-lactones.The optimal reaction conditions were determined to be 2 mol%Re₂O₇as the catalyst and HFIP as the solvent.34biologically activeγ-lactone derivatives including lactones,rearrangement products and spiro rings substituted with fluorine-substituted phenyl.（2）In the second part,this article uses chiral phosphoric acid as a catalyst to catalyze the intermolecular[4+2]reaction between 2-hydroxyphenol and diolefin,and successfully synthesizes benzopyrans.In addition,this article also investigated the effects of catalyst types and solvent types on the enantioselective synthesis of benzopyrans,and determined that 2’-methylspiro[cyclopentane-1,9’-fluorene]is the substituent with chiral phosphoric acid as the best catalyst and toluene as the solvent,the stereoselectivity ee of the synthesized benzopyrans can reach 67%.