【摘 要】
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Over the past few decades,cinchona alkaloids and their derivatives have been demonstrated as privileged chiral catalysts with the sudden explosion of intere
【机 构】
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SchoolofPharmaceuticalScienceandTechnology,DalianUniversityofTechnology,Dalian,116024
【出 处】
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中国化学会第十三届全国有机合成化学学术研讨会
论文部分内容阅读
Over the past few decades,cinchona alkaloids and their derivatives have been demonstrated as privileged chiral catalysts with the sudden explosion of interest in the field of asymmetric catalysis.1 Moreover,phase-transfer catalysis has been recognized as an effective and sustainable method,and cinchona alkaloid based phase-transfer catalysts have been applied to many practical asymmetric syntheses.2 The structures of cinchona alkaloid-based PTCs were usually modified by the esterification of the C-9 hydroxy group or quatemization of the nitrogen atom in the bridge ring.However,to the best of our knowledge,there are no examples of PTCs in which the quinoline nitrogen was oxidized.Our group independently reported an enantioselective α-hydroxylation of β-keto esters with TBHP or CHP as oxidant by a chiral phase transfer catalyst before.3 An efficient and enantioselective photo-organocatalytic α-hydroxylation of β-dicarbonyl compounds by N-oxide PTCs was developed.This simple catalytic procedure is applicable to a wide range of β-keto esters and β-keto amides (23 examples) with a new series of C-2-substituted phase transfer catalysts in good enantioselectivity (up to 83% ee) and yield (up to 99%).Moreover,the reaction was successfully scaled up to gram level without any loss of enantioselectivity.
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