Study On The Synthesis Of Cyclopropanes Catalyzed By Lanthanide Silylamides

Lanthanide bis(trimethylsilyl)amide contains a typical Lewis acid,the lanthanide metal centre,and a typical Bronsted base,the anide.It was found to be efficient catalyst for the phospha-Aldol-Brook rearrangement of ortho-dicarbonyl compounds with dialkyl phosphites.Based on the above results,lanthanide silylamide catalyzed cyclopropanation was studied in this thesis,which is composed of three parts as follows:1.Lanthanide bis(trimethylsilyl)amides[(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 served as efficient catalysts for the one-pot cascade reaction of a-ketoesters,diethyl phosphite and activated alkenes to produce a-dicarbonyl cyclopropanes in moderate to high yields.The reaction is stereoselective and the two adjacent carbonyls linked to the cyclopropane are in the cis-configuration.The high efficiency of the lanthanide amide in catalyzing the reaction is the result of the cooperation between the lanthanide metal center and the N(SiMe3)2 anion.Mechanism studies showed that the cyclopropanes are likely formed via a four-step sequence involving the Pudovik reaction,phospha-Brook rearrangement,Michael addition and intramolecular nucleophilic substitution.2.The one-pot cascade reaction of α-ketoesters,diethyl phosphite and 2-arylmethylene-1,3-indandione catalyzed by[(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 was developed.A series of spiro[cyclopropane-1,2’-indene]-1’,3’-diones were obtained in moderate to high yields.The reaction is stereoselective and the two aryls linked to the cyclopropane are in the trans-configuration.3.The reaction of 1-ethylspiro[indoline-3,2’-oxiran]-2-one with diethyl phosphite catalyzed by[(Me3Si)2N]3Yb(μ-C1)Li(THF)3 was explored.An unexpected product diethyl(1-ethyl-2-oxoindolin-3-yl)phosphonate was obtained and the reason was discussed.