Development of Catalytic Carbene Transfer Reactions Using Alkynes as a Source of Carbenes
Development of Catalytic Carbene Transfer Reactions Using Alkynes as a Source of Carbenes
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DOI：
10.1002/chin.201018237
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发表时间：
2009-11
期刊：
影响因子：
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通讯作者：
K. Ohe;K. Miki
中科院分区：
文献类型：
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作者：
K. Ohe;K. Miki
研究了过渡金属化合物活化炔类原位生成亚乙烯基和亚烷基配合物的方法。通过形成亚乙烯基络合物，然后与炔的相邻亚基电环化来产生环状氧杂卡宾络合物。在研究过程中，发现过渡金属诱导的具有亲核共轭亚基的炔的5-exo-dig环化提供了新型的杂芳烃取代的卡宾络合物，例如（2-呋喃基）-、（2-吡咯基）和（2-噻吩基）卡宾络合物。炔丙基酯的5-exo-dig环化，随后羧酸酯的1，2-迁移导致乙烯基卡宾络合物的形成。金属类卡宾的原位生成具有原子效率高的特点，广泛应用于有机合成中。在这个帐户中，在原位生成的类卡宾物种从一系列的炔和合成应用催化卡宾转移反应，如环加成，成环，叶立德相关的反应，插入反应，环异构化和异构化反应的突出和审查。方案1. MLn在亲核攻击结合炔时的滑移。方案2.通过羰基-烯-炔化合物的环化生成卡宾络合物。方案3.由炔丙基酯生成乙烯基卡宾络合物。2.来自共轭炔的环状卡宾络合物我们报道了基于原位产生亚乙烯基金属，随后进行Saito-Myers型环化，导致自由基物质的共轭无环烯二炔的铑催化环芳构化（方案4）。在我们研究在其他共轭体系中原位生成亚乙烯基复合物的过程中，我们将注意力集中在由具有羰基亚基的共轭炔生成的亚乙烯基复合物的电环化上。用M（CO）5（THF）（M =第6族金属）从炔共轭酯或酰胺1a、B获得苯并吡喃亚基的第一次尝试是不成功的（方案5）。具有烷氧基或氨基的苯并吡喃亚基络合物的形成似乎不足以补偿由于邻位喹啉结构而导致的芳香性损失。用脂肪族C=C键取代芳香族不饱和键使我们发现了一种新的基于原位生成亚乙烯基络合物的6-endo-dig环化。酯或酰胺衍生物2a、B产生黄色结晶亚吡喃基络合物3a、B，作为环状Fischer型氧杂卡宾络合物（方案6）。所选NMR数据总结于表1中。钨络合物3a-W的结构通过X射线晶体学明确确定（图1）。独立地，Iwasawa和同事报道了从1c的酮类似物获得的有趣的苯并吡喃亚甲基络合物（方案7a）。他们还证明了在反应物存在下由1c生成的有趣的含类卡宾的羰基叶立德（含钨的苯并吡喃鎓）的形成（方案7 b）。炔配合物的二分行为是由炔配合物和通过6-endo-dig环化生成的含类卡宾的羰基叶立德之间的快速平衡和通过亚乙烯基环化生成的苯并吡喃亚甲基配合物的不可逆形成来解释的。
The in situ generation of vinylidene and alkylidene complexes based on the activation of alkynes with transition metal compounds was investigated. The cyclic oxacarbene complexes are produced through the formation of vinylidene complexes followed by the electrocyclization with the neighboring subunit of an alkyne. During the course of the study, it was found that a transition metal–induced 5–exo–dig cyclization of alkynes having nucleophilic conjugate subunits affords new types of hetero arene–substituted carbene complexes, such as (2–furyl)–, (2–pyrroryl), and (2–thienyl)carbene complexes. The 5–exo–dig cyclization of propargyl esters followed by 1,2–migration of carboxylates leads to the formation of vinylcarbene complexes. The in situ generation of metal–carbenoid species is highly atom–efficient and widely applicable to organic syntheses. In this account, the in situ generation of carbenoid species from a range of alkynes and synthetic applications to catalytic carbene transfer reactions, such as cycloaddition, annulation, ylide–associated reactions, insertion reactions, cycloisomerization, and isomerization reactions are highlighted and reviewed. Scheme 1. Slippage of MLn in nucleophilc attack to the bound alkyne. Scheme 2. Generation of carbene complexes via cyclization of carbonyl–ene–yne compounds. Scheme 3. Generation of vinylcarbene complexes from propargyl esters. 2. Cyclic Carbene Complexes from Conjugated Alkynes We reported rhodium–catalyzed cycloaromatization of conjugated acyclic enediynes on the basis of the in situ generation of vinylidene–metal followed by Saito–Myers type cyclization leading to radical species (Scheme 4). In the course of our study on the in situ generation of vinylidene complexes in other conjugate systems, we focused our attention on an electrocyclization of vinylidene complexes generated from conjugated alkynes having carbonyl subunits. The first attempt to obtain a benzopyranylidene from an alkyne–conjugated ester or amide 1a,b with M(CO)5(THF) (M = group 6 metals) was unsuccessful (Scheme 5). The formation of a benzopyranylidene complex having an alkoxy or an amino group appeared to be insufficient to compensate for the loss of aromaticity due to the ortho quinonoid structure. Replacement of an aromatic unsaturated juncture with an aliphatic C=C bond led us to find a new 6–endo–dig cyclization based on the in situ generation of a vinylidene complex. Ester or amide derivatives 2a,b produced the yellow crystalline pyranylidene complexes 3a,b as a cyclic Fischer–type oxacarbene complex (Scheme 6). The selected NMR data are summarized in Table 1. The structure of tungsten–complex, 3a–W was unambiguously determined by X–ray crystallography (Figure 1). Independently, Iwasawa and co–workers reported the interesting benzopyranylidene complexes obtained from keto analogue of 1c (Scheme 7a). They also demonstrated the formation of interesting carbenoid–containing carbonyl ylides (tungsten–containing benzopyryliums) generated from 1c in the presence of reactants (Scheme 7b). The dichotomous behavior of the alkyne complex is explained by the rapid equilibrium between an alkyne complex and a carbenoid–containing carbonyl ylide generated via 6–endo–dig cyclization, and the irreversible formation of benzopyranylidene complexes generated via a vinylidene