一种新型可溶性高聚物负载手性配体的合成及其催化烯烃的不对称双羟化反应研究

在碱性条件下, 聚乙二醇单甲醚(HO|OPEG|OMe)与1,4-二氟蒽醌进行亲核单取代反应生成中间体F|AQN-OPEG-OMe, 产率88%. F-AQN-OPEG-OMe与奎宁锂进行亲核取代反应, 以95.6%的产率得到新型手性配体QN|AQN|OPEG-Me. QN-QN|OPEG-Me与OsO4原位配位生成的均相催化剂在4种烯烃的不对称双羟化反应中表现出较高的对映选择性(92%~99%e.e.)和化学产率(80%~94%). 催化活性和立体选择性与Sharpless手性配体(DHQ)2AQN相当. 反应结束后, 配体可用乙醚沉淀回收, 循环使用5次, 催化剂的催化活性和立体选择性无明显改变, 配体的回收率均在95%~97%之间.

Synthesis of a Novel Soluble Polymer-bound Chiral Ligand and It''''s Application in Catalytic Asymmetric Dihydroxylation of Olefins

The osmium catalyzed asymmetric dihydroxylation(AD) of olefins in the presence of cinchona alkaloid derivatives provides one of the most effective methods for the preparation of chiral vicinal diols.Although this reaction has had a widespread application to organic and pharmaceutical synthesis,there have been few large-scale industrial products due to the complicated synthetic manipulations required to produce the chiral ligands.Attachment of the cinchona alkaloid to polymers and recycling of catalyst are of great interest.To realize homogeneous catalysis,in this paper,1,4-difluoroanthraquinone was nucleophilically mono-substituted by HO-OPEG-OMe in the presence of KOH and K_(2)CO_(3)in dry toluene,to give intermediate F-AQN-OPEG-OMe in 88% yield.Then,QN-AQN-OPEG-OMe was obtained in 95.6% yield by reaction of F-AQN-OPEG-OMe with the lithium salt of quinine.The homogeneous catalyst that QN-AQN-OPEG-OMe complexed with osmium tetroxide in situ delivered excellent enantioselectivities(92%-99% e.e.) and good yields(80%-94%) in AD reactions of four olefins,comparable to that of the homogeneous catalyst with Sharpless ligand(DHQ)_(2)AQN reported.This ligand was recovered almost quantitatively by a simple filtration and reused for five cycles without obvious decreased and catalytic activities,with 95%-97% recovery of ligand.