Highly enantioselective direct reductive coupling of conjugated alkynes and α-ketoesters via rhodium-catalyzed asymmetric hydrogenation
Highly enantioselective direct reductive coupling of conjugated alkynes and α-ketoesters via rhodium-catalyzed asymmetric hydrogenation
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DOI：
10.1021/ja056474l
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发表时间：
2006-01-25
影响因子：
15
通讯作者：
Krische, MJ
中科院分区：
文献类型：
--
作者：
Kong, JR;Ngai, MY;Krische, MJ
在丙酮酸乙酯和相关活化酮存在下，使用手性改性的阳离子铑催化剂催化氢化1，3-烯炔1a − 7，导致还原偶联，得到具有优异水平的区域和对映体控制的二烯化α-羟基酯1b − 7和3c − 3f。这些研究代表了第一个高对映选择性的直接催化还原偶联炔酮。如6 b到6c − 6 h的转化所示，含有偶联产物侧链的二烯受到不同的化学和区域选择性操作。使用元素氘还原偶联烯炔6a和丙酮酸乙酯得到单氘代产物氘-6b，这与涉及炔羰基氧化偶联随后氢解裂解所得草胺金属内酯的催化机制一致，这一点通过ESI−MS分析得到证实。
Catalytic hydrogenation of 1,3-enynes1a−7ain the presence of ethyl pyruvate and related activated ketones using chirally modified cationic rhodium catalysts results in reductive coupling to afford dienylated α-hydroxy esters1b−7band3c−3fwith exceptional levels of regio- and enantiocontrol. These studies represent the first highly enantioselective direct catalytic reductive couplings of alkynes to ketones. As illustrated by the conversion of6bto6c−6h, the diene containing the side chain of the coupling products is subject to diverse chemo- and regioselective manipulation. Reductive coupling of enyne6aand ethyl pyruvate using elemental deuterium provides the monodeuterated productdeuterio-6b, consistent with a catalytic mechanism involving alkyne−carbonyl oxidative coupling followed by hydrogenolytic cleavage of the resulting oxametallacycle, as corroborated by ESI−MS analysis.