Direct allylation of aldimines catalyzed by C2-Symmetric N,N′-Dioxide-ScIII complexes:: Highly enantioselective synthesis of homoallylic Amines
Direct allylation of aldimines catalyzed by C2-Symmetric N,N′-Dioxide-ScIII complexes:: Highly enantioselective synthesis of homoallylic Amines
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DOI：
10.1002/chem.200800534
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发表时间：
2008-01-01
影响因子：
4.3
通讯作者：
Feng, Xiaoming
中科院分区：
文献类型：
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作者：
Li, Xing;Liu, Xiaohua;Feng, Xiaoming
光学活性高烯丙基胺是制备生物活性天然产物和相关化合物的有用中间体。[1]亚胺的不对称烯丙化反应提供了直接的途径，人们已致力于设计这种转化的对映选择性版本。[2-4]在这些方法中，亚胺的催化不对称烯丙化反应作为一种更有效的方法，已经取得了重大进展。[5-8]尽管有这些创造性的努力，但新方法的开发、新催化剂的设计和合成仍然面临着相当大的挑战。简化和环境友好的多组分策略已成功地应用于外消旋高烯丙基胺的合成。[10]在这里，我们报道了在温和的条件下，易于获得和可调节的C2对称N，N‘-二氧化物-ScIII络合物促进的醛二胺不对称直接烯丙化反应。手性N，N‘-二氧化物[11-12]及其与不同金属的配合物[13]作为一种用途广泛的催化剂，在羰基化合物和亚胺的对映选择性反应中表现出了优越的性能。在我们对手性N，N‘-二氧化金属络合物催化不对称反应的研究中，它们对烯丙基锡试剂和2-氨基苯酚衍生的醛二胺表现出很好的活化能力。[13]我们试图利用这种催化剂对2-氨基苯酚衍生的醛二胺的不对称烯丙化反应的活化能力，这在Kobayashi，[6]Leighton[3c，d]和Tsogoeva[4d，e]等人的不对称烯丙化反应中得到了很好的证明。以苯甲醛、2-氨基苯酚和烯丙基三丁基锡的三组分反应为基准，考察了不同金属与L合成的N，N‘-二氧化氮L1络合的催化能力。观察到中心金属对反应性和对映体选择性的显著影响，如表1所示。当采用ZrACHTUNGTRENNUNG(OIPR)4[6]和PdACHTUNGTRENUNG(OAc)2[5b-d]时，反应没有发生(表1，条目1，2)。在CuACHTUNGRENNUNG(OTf)2[5h]和InACHTUNGTRENNUNG(OTf)3存在下，以较好的产率得到外消旋产物(表1，条目3，4)。鼓舞人心的是，
Optically active homoallylic amines are useful intermediates for the preparation of bioactive natural products and relevant compounds.[1] The asymmetric allylation of imines provides direct access to them and considerable efforts have been devoted to devising enantioselective versions of this transformation.[2–4] Among these methods, catalytic asymmetric allylation of imines, as a more efficient method, has made significant progress.[5–8] Despite these creative efforts, the development of new methods, the design and synthesis of new catalysts remain considerable challenge. Simplified and environmentally friendly multicomponent strategy [9] has been successfully adopted in the synthesis of racemic homoallylic amines.[10] Herein, we reported an efficient catalytic asymmetric direct allylation of aldimines promoted by readily accessible and tuneable C2-symmetric N, N’-dioxide-ScIII complexes under mild conditions. As a versatile catalyst, chiral N, N’-dioxide compounds [11–12] and their complexes [13] with different metals have showed superiority in the enantioselective reactions of carbonyl compounds and imines. In our study of chiral N, N’-dioxidemetal complexes in catalytic asymmetric reactions, they have exhibited good ability for the activation of allylstannane reagent and 2-aminophenol-derived aldimines.[13] We sought to take advantage of the activation abilities of this kind of catalysts for the asymmetric allylation of 2-aminophenol-derived aldimines, which has been extensively documented well in the allylation by Kobayashi,[6] Leighton [3c, d] and Tsogoeva [4d, e] et al. With the three-component reaction of benzaldehyde, 2-aminophenol and allyltributyltin as benchmark,[14] catalytic ability of different metals complexed with l-proline-derived N, N’-dioxide L1 was tested. The significant effect of the central metal on both reactivity and enantioselectivity was observed, as shown in Table 1. When ZrACHTUNGTRENNUNG (OiPr) 4 [6] and PdACHTUNGTRENNUNG (OAc) 2 [5b–d] were adopted, the reaction did not take place (Table 1, entries 1, 2). Racemic products were obtained with good yields in the presence of Cu-ACHTUNGTRENNUNG (OTf) 2 [5h] and InACHTUNGTRENNUNG (OTf) 3 (Table1, entries3, 4). Inspiringly,