Studies On The Hydroboration Reaction Of Aldehydes And Ketones Catalyzed By Bis(?-diketiminato) Rare-Earth-Metal Amides,Lanthanide Aryloxides And Organolithium Compounds

This dissertation is based on the application of Bis??-diketiminato?Rare-Earth-Metal Amides,lanthanide tris?phenoxide?s and organolithium compounds as catalyst for the hydroboration of aldehydes and ketones.For simplicity,it has been divided into three parts as described below:1?Bis??-diketiminato?Rare-Earth-Metal Amides Catalyzed the Hydroboration and Allylboration of Carbonyl Compounds For the first time,it was shown that?-diimine group-stabilized rare earth amino complexes displayed high catalytic activity towards the hydroboration of carbonyl compounds.The catalytic system was found to be highly efficient and applicable to a wide range of substrate.The kinetic studies of the reaction indicated that the carbonyl compounds and the pinacolborane?HBpin?obeyed the first-order reaction law.In addition,it was found that this catalyst system can also successfully catalyze the allylation of aldehydes with allylboronic acid pinacol ester towards the efficient construction of new C-C bond.2?Studies on the Catalytic Hydroboration of Aldehydes and Ketones by Lanthanide Aryloxides The hydroboration reaction of carbonyl compounds catalyzed by the Ln-O bond such as lanthanide tris?phenoxide?s was explored.Conditions such as reaction solvent,catalyst loading,different central metals,and different sterically hindered ligands were screened.The high activity exhibited by the catalyst system is shown to be related to the aryloxy ligand of the lanthanide tris?phenoxide?s and the central metal.The larger the steric bulk of the ligand,the higher the activity?2,6-^tBu₂-4-MeC₆H₂>2,6-ⁱPr₂C₆H₃>2,6-Me₂C₆H₃?.The larger the radius of the rare earth metal ion,the more favorable the reaction?Nd>Sm>Yb,Y?.Using THF as a solvent at room temperature,0.05 mol%of the catalyst,and 1.1equivalents of pinacolborane?HBpin?,the corresponding borate esters?>99%?were obtained in high yields.Also,this reaction showed good chemoselectivity towards aldehyde vs ketones.DFT calculations were carried out to understand the mechanism of this reaction and the results suggest that the Ln-aryloxide catalysts could effectively trap both substrates,the Ln metal for carbonyl compounds and the aryloxide ligand for HBpin,respectively.Thus,the hydroboration of carbonyl group could occur in a stepwise intramolecular manner via a hydride transfer and the subsequent alkyloxide migration steps to produce the final product.3?Studies on the Catalytic Hydroboration of Aldehydes and Ketones by Organolithium Compounds For the first time,it is shown that organolithium compounds can efficiently catalyze the hydroboration of aldehydes and ketones.Under solventless condition,0.1 mol%of n-butyllithium can rapidly catalyze the complete conversion of a wide range of carbonyl compounds to the corresponding borate esters.Furthermore,studies showed that the system was highly selective towards aldehydes over ketones.This trend was exemplified by electron-donating and electron-withdrawing aldehydes,heterocyclic substrates and also intramolecular substrate bearing both aldehyde and ketone moieties.Other notable features include the use of an inexpensive and easily handled catalyst,low catalyst loading,easy work up,and the potential commercial applications.