Direct catalytic enantioselective aza-Diels-Alder reactions
Direct catalytic enantioselective aza-Diels-Alder reactions
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DOI：
10.1002/anie.200500811
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发表时间：
2005-01-01
影响因子：
16.6
通讯作者：
Córdova, A
中科院分区：
文献类型：
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作者：
Sundén, H;Ibrahem, I;Córdova, A
重要性：虽然间接的，催化的，对映选择性的氮杂-Diels-桤木反应已被报道，本文描述了第一个直接的，有机催化的氮杂-Diels-桤木反应。三种组分，烯酮，甲醛水溶液和胺，与脯氨酸催化剂混合，在许多情况下产生大于94%的对映选择性。当烯酮被B取代时，可分离出Mannich加合物。这表明了一个逐步的机制，其中首先脯氨酸和烯酮形成手性烯胺，其与原位形成的亚胺反应（曼尼希反应）;然后阴离子氮以1，4-方式分子内加成到亚胺离子上，水解导致手性氮杂-狄尔斯-桤木加合物。本文提出了一个三组分反应，其中胺、醛和烯酮的变化可以提供各种对映体富集产物。这份报告应该扩大氮杂-狄尔斯-桤木反应形成含氮化合物的已经很大和重要的领域。类似的有机催化反应，使用亚硝基苯遵循相同的机制，但被称为串联O-亚硝基羟醛/迈克尔反应（Y。Yamamoto，N.
Significance: While indirect, catalytic, enantioselective aza-Diels–Alder reactions have been reported, this paper describes the first direct, organocatalytic aza-Diels–Alder reaction. Three components, enone, aqueous formaldehyde, and amine, are mixed with the proline catalyst and enantioselectivities greater than 94% are produced in many cases. When the enone was bsubstituted, the Mannich adduct was isolable. This indicated a stepwise mechanism where first the proline and enone form a chiral enamine, which reacts with the in situ formed imine (Mannich reaction); the anionic nitrogen then adds intramolecularly in a 1, 4-fashion to the iminium ion and hydrolysis leads to the chiral aza-Diels–Alder adduct.Comment: One-pot reactions are ideal for forming diverse structures with ease. This paper provides a three-component reaction in which variation of amine, aldehyde and enone could provide various enantioenriched products. This report should expand the already large and important field of aza-Diels–Alder reactions to form nitrogen-containing compounds. Similar organocatalytic reactions using nitrosobenzene following the same mechanism were reported, but were termed tandem O-nitroso aldol/Michael reaction (Y. Yamamoto, N.