Regio- and stereoselective synthesis of enamides and dienamides by ruthenium-catalyzed co-oligomerization of N-vinylamides with alkenes or alkynes.
Regio- and stereoselective synthesis of enamides and dienamides by ruthenium-catalyzed co-oligomerization of N-vinylamides with alkenes or alkynes.
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DOI：
10.1002/anie.200701356
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发表时间：
2007-07
影响因子：
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通讯作者：
H. Tsujita;Y. Ura;S. Matsuki;K. Wada;T. Mitsudo;T. Kondo
中科院分区：
文献类型：
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作者：
H. Tsujita;Y. Ura;S. Matsuki;K. Wada;T. Mitsudo;T. Kondo
烯酰胺包含在许多天然产物中，例如水杨卤代酰胺[1]和洛巴他胺[2]，并且最近已经使用过渡金属催化剂合成，如a）酰胺的乙烯基化，[3] B）N-乙烯基酰胺与1，3-丁二烯的螯合辅助偶联反应，[4] c）酰胺与炔的加成，[5] d）烯烃的氧化酰胺化，[6]和e）N-烯丙基酰胺的异构化。[7]二酰胺也是通过Diels-Alder反应制备几种生物碱的重要结构单元。[8]然而，过渡金属介导或催化合成二酰胺的例子仍然很少。[9]在考虑潜在的新方法合成的酰胺和二酰胺，我们已经集中精力在催化的区域和立体选择性的共聚反应。过渡金属催化的烯烃与炔烃共聚合反应已有许多报道。[10]我们也已经开发并报道了烯烃与炔的[2 + 2]环加成反应[11]和线性共聚反应[12]。与此形成鲜明对比的是，除了加氢乙烯化之外，"不同烯烃"的共聚反应仍然相当困难[13]，并且是现代有机化学和有机金属化学中具有挑战性的课题。[14]本文报道了零价正离子催化的烯烃共聚合反应，即N-乙烯基酰胺与烯烃的共聚合反应以及N-乙烯基酰胺、丙烯酸酯和乙烯的共低聚反应，为高区域和立体选择性的烯酰胺的一步合成提供了新的、原子经济的方法。[15如所预期的，本发明的催化剂体系可以应用于N-乙烯基酰胺与炔的共聚合，这使得能够选择性合成二酰胺。（1a，1.1 mmol）与丙烯酸乙酯在催化量的[Ru（η 6-cot）（η 2-dmfm）2]的存在下，（0.020 mmol; cot = 1，3，5-环辛三烯，dmfm =富马酸二甲酯）的N，N-二甲基乙酰胺溶液（DMA，3.0 mL）[14 b，17]在160 ℃下反应3 h，得到线性共二聚体5-（N-甲基乙酰氨基）-辛-4-烯酸乙酯（3a），产率为90%，E选择性为95%[Eq.①]。
Enamides are contained in many natural products such as salicylihalamide [1] and lobatamide,[2] and have recently been synthesized using transition-metal catalysts, as represented by a) the vinylation of amides,[3] b) the chelation-assisted coupling reaction of N-vinylamides with 1, 3-butadiene,[4] c) the addition of amides to alkynes,[5] d) the oxidative amidation of alkenes,[6] and e) the isomerization of N-allylamides.[7] Dienamides are also important building blocks for preparing several alkaloids by the Diels–Alder reaction.[8] However, there are still few examples of transition-metal-mediated or-catalyzed synthesis of dienamides.[9] In considering potential new methods for the synthesis of enamides and dienamides, we have focused our efforts on ruthenium-catalyzed regio-and stereoselective codimerization reactions. Many examples of transition-metal-catalyzed codimerization reactions of alkenes with alkynes have been reported.[10] We also have already developed and reported the reactions of [2+ 2] cycloaddition [11] and linear codimerization reactions [12] of alkenes with alkynes. In sharp contrast, a codimerization reaction of “different alkenes” is still quite difficult except for hydrovinylation [13] and a challenging subject in modern organic and organometallic chemistry.[14] Herein we report zero-valent ruthenium-catalyzed codimerization reaction of different alkenes, that is, a codimerization reaction of N-vinylamides with alkenes as well as a cooligomerization reaction of N-vinylamides, acrylates, and ethylene, which offer novel and atom-economical methods for the synthesis of enamides with high regio-and stereoselectivity in one step.[15, 16] As expected, the present catalyst system can be applied to the codimerization of N-vinylamides with alkynes, which enables the selective synthesis of dienamides.Treatment of N-methyl-N-vinylacetamide (1a, 1.1 mmol) with ethyl acrylate (2a, 1.0 mmol) in the presence of a catalytic amount of [Ru (η6-cot)(η2-dmfm) 2](0.020 mmol; cot= 1, 3, 5-cyclooctatriene, dmfm= dimethyl fumarate) in N, N-dimethylacetamide (DMA, 3.0 mL)[14b, 17] at 1608C for 3 h gave the linear codimer, ethyl 5-(N-methylacetylamino)-pent-4-enoate (3a), in 90% yield with 95% E selectivity [Eq.(1)].