Syntheses Of Polymer With Pendant Of H₈-BINOL And Its Preliminary Application In Asymmetric Catalysis

Over the past decades,optically active 1,1'-bi-2-naphthol?BINOL?derivatives has a wide range of application in many asymmetric reactions and enantiomeric recognition.However,very recent research showed that partially hydrogenated BINOL ligands,5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol?H₈-BINOL?exhibited better chiral inductivity in asymmetric reactions than those obtained from their parent ligand attribute to the steric and electronic modulation in the binaphthyl backbone.Due to most of the reported small molecules chiral catalysts has a rigid process in both product separation and recovery.More attention was focused on the soluble polymer-supported catalyst which has the advantage of recycling.So for,some chiral polymers have been designed and synthesized with pendant of binaphthyl which modified by different groups and applied to a variety of asymmetric catalytic reactions with good enantioselectivity.However,very few H₈-BINOL polymeric chiral catalysts have been synthesized and exhibited effectivity in the asymmetric addition reaction.More recently,our group explored the application of BINOL and its derivatives in the asymmetric reaction.Based on these observations,we reported the synthesis of novel polymeric organocatalysts?L*?with partially hydrogenated aromatic backbone and carried out in asymmetric catalytic research.?1??S?-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol was obtained by reduction of binaphthyls using Pd/C in ethanol solution.In the presence of paraformaldehyde and triethylamine,the formyl group was obtained to produce?S?-3-formyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol.The objective monomer?S?-3-vinyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol was synthesized via Wittig reaction from?S?-3-formyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol.The monomer?S?-3-vinyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol was radically polymerized using AIBN as initiators to get poly[?S?-3-vinyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol] and confirmed to characterize by NMR,FTIR,optical rotation and Gel permeation chromatography.?2?we explored enantioselective inductivity of the Titanium-poly[?S?-3-vinyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol] complexes in the addition of diethylzinc to aromatic aldehydes.Experimental results indicated that the chiral catalyst had good enantioselective inductivity with ee up to 95% subsequently.To further explore the application of the polymer,we studied enantioselective inductivity of the Titanium-poly[?S?-3-vinyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol] complexes in the addition of triethylaluminium to aromatic aldehydes.After the reaction condition being optimized,the addition of benzaldehyde with triethylaluminium had the highest enantioselectivity under the inducement of catalyst and ee was up to 90 %.Also,the poly[?S?-3-vinyl-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol] was recovered simply by pouring into methanol and the recovered polymer could be reused for many times without obvious loss of its enantioselective inducement ability as well as catalytic activity.?3?Two kinds of novel epoxy monomers,?S,S?-3-?glycidyloxy?methyl--5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol and?S,S?-3-?glycidyloxy?-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphtol which derived from?S?-BINOL and?S?-epichlorohydrin,were synthesized and underwent anionic polymerization and deprotection of the MOM groups to obtain soluble polyethers.The enantioselective inducement ability of this polymer is in progress in our laboratory.?4?Seven kinds of polymers were used as the chiral ligands in enantioselective phenylacetylene additions to ketones.Good enantioselectivities were achieved and the effective chiral catalyst could keep the same induction effect after reusing for many times.