Study On The Application Of Phospha-Brook Rearrangement Catalyzed By Lanthanide Silylamides In Cyclization Reaction

The lanthanide silylamides were found to be efficient catalysts for the phospha-Brook rearrangement with ortho-dicarbonyl compounds and dialkyl phosphites,through an umpolung reaction.If a particular electrophile were added to the system,it is expected that cyclic compound would be produced accompanied by the leaving of phosphate group.The lanthanide silylamides catalyzed synthesis of cyclic compounds was studied in this thesis,which is composed of two parts as follows:1.Synthesis of acyl cyclopropane compounds catalyzed by ytterbium silylamideThe tandem reaction of a-ketoformates,diethyl phosphite and activated alkenes can be catalyzed by ytterbium silylamide[(Me3Si)2N]3Yb(?-Cl)Li(THF)3 affording a series of acyl cyclopropane compounds in moderate to excellent yields.The target products were formed via a four-step sequence involving Pudovik reaction,Brook rearrangement,Michael addition and intramolecular nucleophilic substitution.The cooperation of the Lewis acidity and the Bronsted basicity of[(Me3Si)2N]3Ln(?-Cl)Li(THF)3 may be the crucial factor resulting in the efficiency of catalyst.The simple and readily available substrates,mild reaction conditions,and one-pot operation make the reaction an efficient method for the preparation of cyclopropane derivatives.2.Synthesis of spiro[furan-2,3'-indolin]compounds catalyzed by ytterbium silylamideThe reaction of N-ethyl isatin,diethyl phosphite and 2-benzylidene-1,3-diphenylpropane-1,3-diones can be catalyzed by ytterbium silylamide[(Me3Si)2N]3Yb(?-Cl)Li(THF)3 affording a series of spiro[furan-2,3'-indolin]compounds in high yields.The reaction presented here is one-pot and easily handled,and the target products can be synthesized with low catalyst loading under mild reaction conditions.