Study On Hydroboration Of Aldehydes,Ketones And Imines Catalyzed By Rare-earth Silylamides

In this paper,the hydroboration reactions of aldehydes and ketones catalyzed by trisilyl amine-rare earth metal complexes was studied.The mechanism of the reaction was preliminarily explored.In addition,the catalytic behavior of divalent rare-earth metal silylamides for the hydroboration reactions of imines.The main results are as follows:1.Hydroboration reactions of aldehydes and ketones towards pinacolborane catalyzed by trisilyl amine-rare earth metal complexesThe hydroboration reactions of carbonyl compound effectively catalyzed by simple trisilyl amine-rare earth complexes Ln[?SiMe₃?₂]₃?Ln = Yb,Y,Eu,Sm,Nd,La?under mild conditions.The solvent,the loading of catalyst,type of catalyst and reaction time were systematically screened.The results show that the largest radius La[?SiMe₃?₂]₃ has the highest catalytic activity.when the catalyst loading is 0.1 mol%,room temperature for 10 min,Most of the substrate conversion rate can reach more than 90%.The catalytic system has good universality for substrates,whether aromatic or aliphatic aldehydes and ketones,or compounds containing heterocyclic structures,can maintain very high catalytic activity of the substrate.2.Hydroboration reactions of imines towards pinacolborane catalyzed by divalent rare-earth metal silylamidesAs a kind of good single electron reagent,the divalent rare earth metal complex has a strong reductive property.Divalent rare-earth metal silylamides Yb[?SiMe₃?₂]₂ effectively catalyze the hydroboration reactions of imines under mild conditions.The solvent,catalyst type and loading,reaction temperature,reaction time and so on were screened systematically.The results show that when the amount of catalyst is 5 mol% and the reaction time is 3 hours at 40 ?,the conversion rate of most imines can reach above medium.Compared with most of the catalytic systems currently reported,the reaction time is shortened greatly and the yield of the reaction is increased.The electron-withdrawing group is more favorable to the catalytic activity than the electronic-donating group.The steric resistance effect may hinder the reaction,but the conversion rate can be improved by prolonging the reaction time.