Tris(Bis (Trimethylsilyl) Amino) Lanthanide Complexes And The Deprotonated ?-ketoimine Lithium Compound And Their Application In Hydroboration

In this paper,the hydroboration of esters catalyzed by tris(bis(trimethylsilyl)amino)lanthanide complexes was investigated.Besides,catalyst-free and solvent-free hydroboration of carboxylic acids was studied.Finally,the deprotonated phenyl-bridged ?-ketoimine lithium compound was synthesized and characterized,and it's catalytic behavior was also examined.The main results obtained are as follows:1.Homoleptic lanthanide amides Ln[N(SiMe3)2]3 demonstrated excellent catalytic activity in the hydroboration of esters using pinacolborane(HBpin)as the reducing agent.The reaction conditions,such as the ratio of reaction substrate,solvent,catalyst loading and different rare earth metals,were screened.The experiments show that the radius of the rare earth ions has a great influence on the progress of the reaction(La>Nd>Sm>Eu>Y>Yb).The larger the radius,the faster the reaction rate.Using 0.5-5 mol%La[N(SiMe3)2]3 as a catalyst,aromatic,aliphatic esters and lactones with HBpin,respectively,can be almost completely converted to the boronic esters without solvent at room temperature.Pleasingly,La[N(SiMe3)2]3 showed broad functional group compatibility and good chemoselectivity.Furthermore,La[N(SiMe3)2]3 is capable to realize the very challenging and rarely reported hydroboration of carbonate esters with low catalyst loading at room temperature.Both cyclic and linear carbonate esters can be easily converted to the corresponding products.Besides,the hydroboration of alkynes has been developed by using La[N(SiMe3)2]3 as the catalyst.The experiment showed that esters were more reactive than alkynes.Mechanistic postulation for the ester hydroboration was supported by DFT calculations.2.We unexpectedly found a facile method for deoxygenative hydroboration toward a broad range of carboxylic acids under very mild conditions.The most striking feature of this attractive hydroboration is that this elusive and challenging transformation was realized without catalyst and solvent,and the primary or secondary alcohol was then obtained through hydrolysis.Solvent effect investigation showed that THF was also suitable for this kind of reaction.Moreover,a successful gram-scale trial may provide a very promising toolkit for carboxylic acid reduction at large scale.3.The reaction of the phenyl-bridged ?-ketoimine ligand with different equivalents of n-butyllithium can produce lithium compounds with different structures.when the ratio of the two is 1:4,a deprotonated ?-ketoimine tetralithium compound is gained.This provides a simple and convenient method for the synthesis of deprotonated?-ketoimine compounds,and this new type of lithium ?-ketoimine compound also has a good application in the hydroboration reaction.