Cooperative Catalysis of Primary and Tertiary Amines Immobilized on Oxide Surfaces for One-Pot C-C Bond Forming Reactions
Cooperative Catalysis of Primary and Tertiary Amines Immobilized on Oxide Surfaces for One-Pot C-C Bond Forming Reactions
复制标题
DOI：
10.1002/anie.200802515
复制
发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Iwasawa, Yasuhiro
中科院分区：
文献类型：
--
作者：
Motokura, Ken;Tada, Mizuki;Iwasawa, Yasuhiro
多催化功能的发展使得在均相和多相催化剂体系中进行高效的有机合成成为可能。[1]近年来，具有化学设计表面的负载型催化剂不仅作为可回收的试剂，而且作为多功能表面材料而受到极大的关注。[2，3]这些多功能催化剂可以实现一锅反应[2]，并协同促进单一反应步骤。[3]有几个报告表明，多相催化剂表面具有多官能位，可促进有机合成。[4，5]然而，仍需要明确的例子在表面协同多功能催化碳-碳键形成反应。从基础和工业的角度来理解表面高效多功能催化的合成策略。叔胺是亲核剂活化的路易斯碱和布朗斯特碱。相反，负载伯胺可以有效地催化羰基化合物的缩合反应，如硝基-羟醛缩合反应[6]，其中伯胺被认为通过形成亚胺中间体来激活羰基化合物。[4C，6]这些事实表明，叔胺和伯胺固定在同一固体表面上，可以通过活化亲核试剂和亲电剂，为有机C？C成键反应创建有效的多相催化剂。在有组织的固定化体系中，表面酸中心也可能有助于促进表面反应。在这里，我们报道了第一个例子，多相组合叔胺和伯胺催化剂，固定在硅铝(SA)上，具有极高的效率一锅合成1，3-二硝基烷烃。我们考察了苯甲醛(1)和硝基甲烷(2)在各种异相和均相胺存在下的反应，如表1所示。在几乎所有的情况下，2-硝基苯乙烯(3)都是主要产物。与其他胺催化剂相比，双胺催化剂(SA-NH2-NEt2-A-D，见实验部分)表现出较高的初始转化率1(表1，条目1和2)。含有伯胺和叔胺(正己胺和三乙胺)混合物的均相溶液，在SA-NH2-NET2-B中相当于NH2和NET2，比SA负载的多相催化剂活性低得多(表1，条目11)。向溶液中添加SA可略微改善低活性(表1，条目9)。使用具有与SA-NH2-NEt2-B相似的胺负载量的SA-NH2和SA-NEt2的反应以非常低的转化率进行(表1，条目7和8)。在SA-NH2和SA-NET2的物理混合物的情况下，
The development of multicatalytic functions enables highly efficient organic syntheses in both homogeneous and heterogeneous catalyst systems.[1] Recently, supported catalysts with chemically designed surfaces have received much attention, not only as recoverable reagents, but also as multifunctional surface materials.[2, 3] These multifunctional catalysts can enable one-pot reaction sequences [2] and cooperatively promote single-reaction steps.[3] There are several reports of heterogeneous catalysts having multifunctional sites on their surfaces, which promote organic synthesis.[4, 5] Nevertheless, clear examples of cooperative multifunctional catalysis at surfaces for carbon–carbon bond-forming reactions are still required, to understand the synthetic strategy of efficient multifunctional catalysis at surfaces from fundamental and industrial points of view.Tertiary amines act as Lewis and Brønsted bases for the activation of nucleophiles. Conversely, supported primary amines efficiently catalyze condensation reactions of carbonyl compounds, such as nitro-aldol reactions,[6] in which the primary amines are thought to activate the carbonyl compounds through formation of imine intermediates.[4c, 6] These facts suggest that the immobilization of both tertiary and primary amines onto the same solid surface can create an efficient heterogeneous catalyst for organic CÀC bondforming reactions by activation of both nucleophiles and electrophiles. In an organized ensemble of the immobilized system, surface acid sites may also contribute to promotion of the surface reactions. Herein, we report the first example of a heterogeneous combined tertiary and primary amine catalyst, immobilized on silica–alumina (SA), with tremendous efficiency for the one-pot synthesis of 1, 3-dinitroalkanes. We examined the reaction between benzaldehyde (1) and nitromethane (2) in the presence of various heterogeneous and homogeneous amines, as shown in Table 1. In almost all cases, 2-nitrostyrene (3) was obtained as a main product. The double-amine catalysts (SA–NH2–NEt2-A–D, see Experimental Section) showed high initial conversion rates of 1 compared with other amine catalysts (Table 1, entries 1 and 2). A homogeneous solution containing a mixture of the primary and tertiary amines (n-hexylamine and triethylamine), in equivalent amounts to NH2 and NEt2 in SA–NH2–NEt2-B, was much less active than SA-supported heterogeneous catalyst (Table1, entry11). The low activity was slightly improved by the addition of SA into the solution (Table 1, entry 9). The reactions using SA–NH2 and SA–NEt2 with similar amine loadings to those in the SA–NH2–NEt2-B proceeded at very low conversion rates (Table 1, entries 7 and 8). In the case of a physical mixture of SA–NH2 and SA–NEt2,