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首页> 外文期刊>Chemistry: A European journal >Asymmetric Synthesis of Oxygen Heterocycles via Pd-Catalyzed Dynamic Kinetic Asymmetric Transformations:Application of Nucleosides
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Asymmetric Synthesis of Oxygen Heterocycles via Pd-Catalyzed Dynamic Kinetic Asymmetric Transformations:Application of Nucleosides

机译：通过Pd催化的动态动力学不对称转化的氧杂环的不对称合成：核苷的应用

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摘要

Racemic butadiene and isoprene monoepoxide react with unsaturated alcohols in the presence of a chiral palladium catalyst and a boron co-catalyst to give 3-allkoxy-4-hydroxy-1-butene and 3-alkoxy-4-hydroxy-3-methyl-1-butene,respectively,with excellent regioand enantioselectivity in a dynamic kinetic asymmetric transformation whereby both enantiomers of the starting epoxides provide the same enantiomeric product.In the case of 2-phenylbutadiene monoepoxide,easily available from phenacyl chloride and vinylmagnesium bromide,the reaction proceeds by kinetic resolution.A model to rationalize the result is presented.The bis-olefin products are ideal substrates for the Ru catalyzed ring closing metathesis.In this way,five-,six-,and sevenmembered oxygen heterocycles are readily available enantiomerically pure.The value of this very simple two step process is demonstrated by the use of the five-membered ring heterocycles to form unnatural and unusual nucleosides that cannot be easily accessed by other means.The sequence involvesa Ru catalyzed isomerization of the initial 2,5-dihydrofuran to a 2,3-dihydrofuran followed by a selenium promoted addition of pyrimidine or purine base.One advantage of this strategy is the easy access to either enantiomeric serices,both of which have important biological applications.
机译：外消旋丁二烯和异戊二烯单环氧化物在手性钯催化剂和硼助催化剂的存在下与不饱和醇反应，生成3-烷氧基-4-羟基-1-丁烯和3-烷氧基-4-羟基-3-甲基-1 -丁烯在动态动力学不对称转化中分别具有优异的区域和对映选择性，因此起始环氧化物的两种对映异构体均提供相同的对映体产物。对于2-苯基丁二烯单环氧化物，可轻松地从苯甲酰氯和乙烯基溴化镁中获得，该反应通过动力学拆分。提出了一个使结果合理化的模型。双烯烃产物是Ru催化的闭环易位的理想底物。这样一来，五，六和七元氧杂环很容易获得对映体纯。通过使用五元环杂环形成不容易获得的非天然和异常核苷，可以证明这一非常简单的两步过程该序列涉及Ru催化的将最初的2,5-二氢呋喃异构化为2,3-二氢呋喃，然后通过硒促进的嘧啶或嘌呤碱的加成反应。该策略的优势之一是易于获得对映体，两者都有重要的生物学应用。

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