Asymmetric Michael Addition Reaction And Hydrophosphonylation Catalyzed By Rare Earth Metal Complexes Bearing Phenoxy Functionalized Chiral Diphenylprolinolate Ligands

A series of rare earth metal complexes bearing phenoxy functionalized chiral diphenylprolinolate ligands were synthesized and their catalytic properties for asymmetric Michael addition and hydrophosphonylation reaction were investigated.I. Synthesis of rare earth metal complexes 1-5 bearing phenoxy functionalized chiral diphenylprolinolate ligandsReactions of RE[N(Si Me3)2]3(RE = Yb, Y, Sc) with H2 L in a 1:2 molar ratio in THF gave the corresponding rare earth metal complexes L1RE(L1H)(H2L1 =(S)-2,4-di-tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl) phenol, RE = Yb(1), Y(2), Sc(3)) and L2Sc(L2H)(4)(H2L2 =(S)-2,4-di-dimethylbenzyl-6-((2-(hydroxy-diphenylmethyl)-pyrrolidin-1-yl)methyl)phenol)) in good isolated yields. The structures of them were well characterized, including X-ray determination for complex 3.Reaction of anhydrous ScCl3 with L1Li2 in a 1:2 molar ratio in THF gave the scandium chloride L1 Sc Cl(THF)(5)(H2L1 =(S)-2, 4-di-tert-butyl-6-((2-(hydroxy diphenylmethyl)pyrrolidin-1-yl)methyl)phenol) in good isolated yields.II. Asymmetric Michael addition of malonates to unsaturated ketones catalyzed by rare earth metal complexes 1-4A simple, efficient catalytic asymmetric Michael addition of malonates to unsaturated ketones has been successfully developed. This process was promoted by 10 mol% rare earth metal complexes 1-4 bearing chiral phenoxy functionalized prolinol ligand without additive at room temperature,reaching the products with good to excellent yield(80-99%) and medium to good enantioselectivity(77-90%). Most of the substrates was applicable for the catalyst system well, especially for the substrates with large steric hindrance. This result well expand the application of rare earth metal catalysts in the asymmetric Michael addition.III. Asymmetric hydrophosphonylation reaction of unsaturated ketones catalyzed by rare earth complex 5Complex L1 Sc Cl(THF)(5) was found to be highly efficient catalyst for enantioselective hydrophosphonylation of a,β-unsaturated ketones, which gave the corresponding chiral products with excellent yields and good enantioselectivities in DME with TMEDA at 0 o C. The TMEDA was found to act as a co-catalyst in the reaction based on the research of the loading sequence. The further study of the reaction is still underway.IV. Asymmetric epoxidation of unsaturated ketones catalyzed by heterobimetallic rare earth metal- lithium complexes bearing phenoxy-functionalized chiral diphenylprolinolate ligandFour novel heterobimetallic complexes [REL12]{[(THF)3Li]2(μ-Cl)} stabilized by chiral phenoxy-functionalized prolinolate(RE = Yb(6), Y(7), Sm(8), Nd(9)) have been synthesized. These readily available complexes were found to be highly active in catalyzing the epoxidation of α,β-unsaturated ketones, according to the previous work, we completed the exploring of the scope of substartes and got the epoxides in 60-79% yield and 80>99% ee.