Synthesis Of Planar Chiral[2.2]Paracyclophanyl Imidazolium Saltsbearing Crown Ether And Their Application In Asymmetric Catalysis

Although the application of planar chiral [2.2]paracyclophane compounds in asymmetric synthesis until the early1990s began, the planar chiral ligands have been a wide range of applications in asymmetric catalytic reactions and have achieved some good results in a short span of20years. Catalytic asymmetric formation of C-C bonds has been the organic chemistry topic at the forefront, also diaryl-methanol and its derivatives as the precursor of pharmaceutical intermediates have great significance. Therefore, the asymmetric1,2-addition of arylboronic acid to aldehydes has attracted much attention from chemists. In1998, Miyaura reported the addition of the rhodium-catalyzed arylboronic acid to aldehyde for the first time. Arylboronic acid functional group which is compatibility, water and air stability, low toxicity, etc., is becoming an important topic of recent research. N-heterocyclic carbenes (NHCs)whose catalytic effect is not lost on the phosphine ligand have been succesfully employed in various homogeneous metal-catalyzed reactions,so this will also be the direction of our efforts.For these reasons above mentioned, we designed and synthesized a new family of planar chiral [2.2] paracyclophane imida-zolium salts, and employed them in the asymmetric1,2-addition of arylboronic acid to aldehydes as carbene precursors.This thesis is divided into nine parts, the main contents are as follows:1.[2.2] paracyclophane synthesisPreparation of [2.2]paracyclophanes via Hofmann elimination:first in the strong alkaline conditions, the para-methylbenzyl trimethylammonium chlo-ride was dimerization of two molecules of unstable intermediates to produce [2.2] paracyclophane.2.4,16-dibromo[2.2]paracyclophane synthesisUse of bromide of iron as a catalyst and dichloromethane as solvent,[2.2]para-cyclophanes and bromine reacted to give4,16-dibromo[2.2]paracyclophane.4,16-dibromo[2.2]paracyclophane. 3.4,12-dibromo[2.2]paracyclophane synthesis4,16-dibromo[2.2]paracyclophane transformed to4,12-dibromo[2.2]paracyclophane in n-dodecane at230℃.4.4-amino-12-bromo[2.2]paracyclophane synthesis and resolution4-Dibenzophenone imine-12-bromo[2.2]paraparacyclophane was obtained by treatment of4,12-dibromo[2.2]paracyclophane with benzophenone imine, in the presence of sodium tertbutoxide and Pd-DPPF catalyst. Then it is hy-drolyzed by HCl in THF to give4-amino-12-bromo[2.2]paracyclophane. The resolution of4-amino-12-bromo[2.2]paracyclophane was achieved to produce. Rp-(-)-4-amino-12-bromo[2.2]paracyclophane5. Synthesis of Rp-N,N’-bis(12-bromo-4-[2.2]pavacyclophane) imidazolium triflu-oromethanesulfonate4-Amino-12-bromo[2.2]paracyclophanes in THF reacted with40%glyoxal aque-ous solution to afford diimine. The diimine was treated with the soultion of silver triflate and chloromethyl pivalate in dark at room temperature to form the imidazole tri?uoromethylsulfonate.6. Synthesis of Rp-N,N’-bis(12-methoxy-4-[2.2]paracyclophane) imidazole triflu-oromethanesulfonateFrom Rp-4-amino-12-bromo[2.2]paracyclophane starting material, via diazoti-zation, alkaline hydrolysis, methylation, amination, hydrolysis, condensation and ring closing seven-step reaction, the target compound can be obtained.7. Synthesis of cyclophane imidazolium trifluoromethanesulfonates bearing the crown ethers and the pyridyl crown etherRp-4-hydroxy-12-brorao[2.2]paracyclophane as the starting material, via ether-ification with the Bis(para-toluenesulfonate) of corresponding diol and2,6-pyridine-dimethol, amination, hydrolysis, condensation and cyclization reac-tion, transformed to the corresponding target products.8. Synthesis of paracyclophanyl imidazolium trifluoromethanesulfonate bearing methanesulfonateRp-4-acetyl oxygen-12-bromo[2.2]paracyclophane as the starting material, via amination, esterification with the methanesulfonyl chloride, condensation and cyclization provided the target carbene precursor.9. Catalytic research:the above imidazoliums were used as ligands in the carbene-Rh catalyzed asymmetric1,2-addition of arylboronic acid to aldehydes.Innovative in this paper:1. A family of imidazolium salts, including novel imidazoliums bearing pyridyl and Sulfonates were synthesized for the first time.2. The imidazoliums were used as ligands in carbene-Rh catalyzed asymmetric addition of arylboronic acid to aldehydes to afford chiral secondary alcohols with high yields and moderate enantioselectivities.