Enantioselective reductive cyclization of 1,6-enynes via rhodium-catalyzed asymmetric hydrogenation: C-C bond formation precedes hydrogen activation
Enantioselective reductive cyclization of 1,6-enynes via rhodium-catalyzed asymmetric hydrogenation: C-C bond formation precedes hydrogen activation
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DOI：
10.1021/ja042645v
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发表时间：
2005-05-04
影响因子：
15
通讯作者：
Krische, MJ
中科院分区：
文献类型：
--
作者：
Jang, HY;Hughes, FW;Krische, MJ
使用手性改性阳离子铑预催化剂对 1,6-烯炔进行不对称氢化，能够实现对映选择性还原环化，以完全原子经济的方式提供亚烷基取代的碳环和杂环。在一组结构多样的底物中观察到良好到优异的产量和异常水平的不对称诱导。涉及氢-氘交叉实验的机理研究，以及对非共轭环异构化产物14c和15c的观察表明，铑(III)金属环戊烯的形成发生在氢活化之前。这种氧化偶联-氢解裂解基序应该在相关氢介导偶联的设计中发挥关键作用。
Asymmetric hydrogenation of 1,6-enynes using chirally modified cationic rhodium precatalysts enables enantioselective reductive cyclization to afford alkylidene-substituted carbocycles and heterocycles in a completely atom economical fashion. Good to excellent yields and exceptional levels of asymmetric induction are observed across a structurally diverse set of substrates. Mechanistic studies involving hydrogen−deuterium crossover experiments, along with the observance of nonconjugated cycloisomerization products14cand15c, suggest rhodium(III) metallocyclopentene formation occurs in advance of hydrogen activation. This oxidative coupling−hydrogenolytic cleavage motif should play a key role in the design of related hydrogen-mediated couplings.