手性噁唑硼烷催化芳基磷氧对α,β-双功能不饱和化合物的不对称膦氢化反应研究  

Asymmetric Hydrophosphination of Diarylphosphine Oxides toα,β-Unsaturated Bifunctional Compounds Catalyzed by Chiral Oxazaborolidine

作　　者：高琦 陈丽蓉 钱金一 樊瑞峰 孙蔚青[1] 郭亚飞 樊保敏[1] Gao Qi;Chen Lirong;Qian Jinyi;Fan Ruifeng;Sun Weiqing;Guo Yafei;Fan Baomin(Yunnan Key Laboratory of Chiral Functional Substance Research and Application,Yunnan Minzu University,Kunming 650500,China;Key Laboratory of Chemistry in Ethnic Medicinal Resources,Ministry of Education,Yunnan Minzu University,Kunming 650500,China)

机构地区：[1]云南民族大学云南省手性物质研究与利用重点实验室,昆明650500 [2]云南民族大学民族药资源化学教育部重点实验室,昆明650500

出　　处：《化学学报》2024年第7期742-747,共6页Acta Chimica Sinica

基　　金：国家自然科学基金(Nos.22361053,21961045);云南省基础研究计划(Nos.202301AU070125,202401BC070018);云南省手性物质研究与利用重点实验室项目(No.202402AN360010);云南省“兴滇英才”青年专项项目资助.

摘　　要：手性噁唑硼烷催化剂(CBS)作为一种经典的非金属催化剂,被广泛地用于酮的不对称还原和不对称环加成反应.本工作报道了一种使用CBS催化剂,实现二芳基磷氧亲核试剂对α,β-双功能不饱和化合物的不对称Michael加成反应.该反应的可能催化机理与早期报道的CBS催化机理不同,CBS在此反应中很有可能是作为一个路易斯酸碱对,通过裂解亲核试剂的氢氧键,进而通过协同加成的过程,实现不对称膦Michael加成反应.另外,该反应具有底物适用性良好、反应条件温和(室温)、对空气水分不敏感、易于放大等优点,在合成手性膦配体领域具有潜在的应用价值.Oxazaborolidines(CBS)have been widely utilized as organocatalysts in enantioselective organic synthesis over the past thirty years,particularly for the asymmetric reduction of ketones and enantioselective cycloaddition reactions.The history of oxazaborolidines functioning as chiral Lewis acids has demonstrated that CBS requires activation by strong pro-tonic acids or Lewis acids to enhance the Lewis acidity of boron,such as TfOH,Tf_(2)NH,and AlBr_(3).In our previous work,we introduced a new application of CBS in the asymmetric 1,4-addition of diarylphosphine oxides toα,β-unsaturated ketones and esters.Unlike traditional CBS-catalyzed reactions,this catalytic system does not require strong protonic acids or Lewis acids to activate CBS;instead it likely functions as a Lewis pair to cleave the O—H bond and provide a chiral phosphorous inter-mediate.To further expand the application of this new method,we selectedα,β-unsaturated bifunctional compounds bearing both a ketone and an amide group on either side of the double bond as substrates for this study.Initially,several oxazaboroli-dines and reaction conditions were explored for the model reaction.The results indicated that under optimal conditions(20 mol%Me-CBS at room temperature in acetonitrile for 2 h),the reaction proceeded well with high yield(99%)and high enan-tiomeric excess(93%ee).Subsequently,various substrates were examined under these optimal conditions yielding products with 52%~99%yields and 63%~99%ee.The general procedure involved stirring a mixture of substrates(0.24 mmol,1.2 equiv.),diarylphosphine oxides(0.2 mmol,1 equiv.),and CBS(20 mol%Me-CBS)in 2 mL acetonitrile for 2 h followed by purification via flash column chromatography.Finally,the potential mechanism behind how the catalyst functions as a Lewis pair to control enantioselectivity was discussed.Additionally,the chiral products have potential applications in synthesizing valuable phosphine ligands.

关 键 词：噁唑硼烷 芳基磷氧 α β-不饱和化合物 不对称膦氢化 

分 类 号：O621.251[理学—有机化学]