Study On Synthesis Of Cyclopenta[c]furo[3,2-b]pyranone And Disubstituted Dihydrofuran-2(3H)-one

The paper mainly discusses the following two aspects.First,silver（I）-catalyzed synthesis cyclopenta[c]furo[3,2-b]pyranone starting from conjugated ene-yne-ketones（ester,sulfone,phospholipid）have been exploited.Second,rhodium-catalyzed synthesis of disubstituted dihydrofuran-2（3H）-one starting from 6-bromo-2-diazo-3,7-dioxo-5,7-diphenylheptanoic acid ester（ketone）were studied.The paper is divided into three parts for discussion.The first chapter is a review of the literature about the transition metal-catalyzed carbene cross-coupling,migration,insertion and other related reaction ofα-diazo carbonyl compounds.In the second chapter,AgBF₄-catalyzed cyclization of two molecules of acetylene ketone（ester,sulfone,phosphonate）is exploided to synthesize a series of novel heterocyclic compound,i.e.cyclopenta[c]furo[3,2-b]pyranone,for the first time.The optimized conditions were obtained as below:10 mol%silver tetrafluoroborate as catalyst,anhydrous 1,2-dichloroethane as solvent,reaction temperature25 ^oC under nitrogen atmosphere.Under optimized reaction conditions,the yield is from 40%to 85%.The advantages of this method are mild conditions,simple operation and high selectivity.A reasonable mechanism of the reaction was proposed on the basis of our experimental results and investigations in literature.First,the formation of Argentum（I）（2-furyl）carbene starting from one molecule of ene-yne-ketones（ester,sulfone,phosphonate）,and then regioselective[4+2]cycloaddition of the（2-furyl）carbene with another molecule of ene-yne-ketones（ester,sulfone,phosphonate）constructs cyclopenta[c]furo[3,2-b]pyranone.In the third chapter,the aldol condensation reaction of enolate titaniumreagentderivedfromdiazoacetylacetonewithα-bromo-α,β-unsaturated ketone was investigated.The 1,2 and 1,4addition regioselectivity can be controlled by using the different Lewis acids.Then,ruthenium-catalyzed cyclization of 6-bromo-2-diazo-3,7-dio-xo-5,7-disubstituted heptanoate（ketone）is investigated,affording disubstituted dihydrofuran-2（3H）-one.The optimized conditions for this transformation were as below:10 mol%Rh₂（OAc）₄ as catalyst,toluene as solvent,reaction temperature 25 ^oC under nitrogen atmosphere.Under the optimal conditions,a varity of substrates can be applied to the efficient synthesis of the disubstituted dihydrofuran-2（3H）-one.This novel method for the synthesis of the disubstituted dihydrofuran-2（3H）-one has the advantages of mild conditions,simple operation and exccelent selectivity.The yield is between 50%and 83%.This is a novel synthetic strategy for diastereoselectiveconstructionofthedisubstituted dihydrofuran-2（3H）-one.