Enantioselective iridium-catalyzed vinylogous Reformatsky-aldol reaction from the alcohol oxidation level: linear regioselectivity by way of carbon-bound enolates.
Enantioselective iridium-catalyzed vinylogous Reformatsky-aldol reaction from the alcohol oxidation level: linear regioselectivity by way of carbon-bound enolates.
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对映射的虹膜选择性催化的乙烯基乙烯基毒性重构 - 醇氧化水平的反应：通过碳结合的方式进行线性区域选择性。
DOI：
10.1002/anie.201100646
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发表时间：
2011-04-04
影响因子：
16.6
通讯作者：
Krische, Michael J.
中科院分区：
文献类型：
--
作者：
Hassan, Abbas;Zbieg, Jason R.;Krische, Michael J.
醛醇缩合反应中的乙烯基葡萄糖[1]是一类重要的羰基加成反应。[2]绝大多数的对映选择性乙烯基羟醛加成使用衍生自β-酮酯[3]的二烯醇化物和二烯醇醚与手性刘易斯酸、[3a-k]手性刘易斯碱、[3 k-m]或手性氢键供体组合。[3n]衍生自简单α，β-不饱和羰基化合物[3 k-m，4]和2-甲硅烷氧基呋喃[5]的二烯醇酯和二烯醇醚也参与对映选择性乙烯基羟醛加成。虽然在某些情况下已经获得了优异的区域选择性和对映体选择性，但所需二烯醇醚的形成和易处理性对其使用构成了障碍。另外，甲硅烷基二烯醇醚的手性刘易斯酸催化的反应经常遭受竞争外消旋甲硅烷基阳离子催化的背景反应，因此需要缓慢加入二烯醇醚、低温条件和高催化剂负载。未改性的不饱和羰基化合物的乙烯基直接羟醛加成可能解决这些限制，[6]然而，迄今为止，这种转化仅限于使用2-（5 H）-呋喃酮或腈作为羟醛供体。[6，7]与现有技术显著不同的是，Kanai、Shibasaki和同事设计了由频哪醇硼烷介导的丙二烯酯的还原乙烯基羟醛缩合反应。[8]一个相关的还原过程，乙烯基Reformatsky反应，可能会提供相同的产品，然而，对映选择性的变体是未知的。[9]在本文中，在C-C键形成转移氢化的条件下，[10，11]我们报道了对映选择性乙烯基Reformatsky型加成的第一个实例，并建立了催化条件，其中不对称羰基加成以与醇或醛氧化水平相同的便利性发生（方案1）。
Vinylogues [1] of the aldol reaction represent an important class of carbonyl addition processes.[2] The vast majority of enantioselective vinylogous aldol additions employ dienolates and dienol ethers derived from β-ketoesters [3] in combination with chiral Lewis acids,[3a–k] chiral Lewis bases,[3k–m] or chiral hydrogen-bond donors.[3n] Dienolates and dienol ethers derived from simple α, β-unsaturated carbonyl compounds [3k–m, 4] and 2-siloxy furans [5] also participate in enantioselective vinylogous aldol additions. While excellent regio-and enantioselectivities have been obtained in certain cases, the formation and tractability of the requisite dienol ethers pose a barrier to their use. Additionally, chiral Lewis acid catalyzed reactions of silyl dienol ethers often suffer from competing racemic silyl cation catalyzed background reactions, thus requiring slow addition of the dienol ether, cryogenic conditions, and high catalyst loadings. Vinylogous direct aldol additions of unmodified unsaturated carbonyl compounds potentially address these limitations,[6] however, to date, such transformations are restricted to the use of 2-(5H)-furanones or nitriles as aldol donors.[6, 7]In a significant departure from prior art, Kanai, Shibasaki, and co-workers devised a reductive vinylogous aldol reaction of allenic esters mediated by pinacolborane.[8] A related reductive process, the vinylogous Reformatsky reaction, could potentially deliver identical products, however, enantioselective variants are unknown.[9] Herein, under the conditions of C–C bond-forming transfer hydrogenation,[10, 11] we report the first examples of enantioselective vinylogous Reformatsky-type additions, and establish catalytic conditions wherein asymmetric carbonyl addition occurs with equal facility from the alcohol or aldehyde oxidation level (Scheme 1).
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影响因子：
16.6
作者：
Bower, John F.;Kim, In Su;Patman, Ryan L.;Krische, Michael J.
通讯作者：
Krische, Michael J.
影响因子：
2
作者：
Denmark, SE;Heemstra, JR
通讯作者：
Heemstra, JR
影响因子：
15
作者：
Denmark, SE;Beutner, GL
通讯作者：
Beutner, GL
影响因子：
--
作者：
Bower, John F.;Krische, Michael J.
通讯作者：
Krische, Michael J.
影响因子：
1.8
作者：
Curti, Claudio;Sartori, Andrea;Casiraghi, Giovanni
通讯作者：
Casiraghi, Giovanni