Cobalt-Mediated Intermolecular Allyl/Alkyne [3 + 2 + 2] Cycloaddition Reactions. A Practical Metal Template for Convergent Synthesis of Functionalized Seven-Membered Rings
Cobalt-Mediated Intermolecular Allyl/Alkyne [3 + 2 + 2] Cycloaddition Reactions. A Practical Metal Template for Convergent Synthesis of Functionalized Seven-Membered Rings
复制标题
钴介导的分子间烯丙基/炔烃 [3 2 2] 环加成反应。
DOI：
10.1021/ja982010u
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发表时间：
1998
影响因子：
15
通讯作者：
J. Stryker
中科院分区：
文献类型：
--
作者：
N. Etkin;Trevor L. Dzwiniel;Kathy E. Schweibert;J. Stryker
过渡金属介导的环加成反应提供了合成重要的有机环体系的途径，这是传统的环加成方法无法实现的。2七元环合成是其中最重要的一环，在二组分环加成反应和分子内环化方法学方面取得了重要进展。3针对分子间三组分的环化反应，我们的研究重点是金属介导烯丙基/炔环加成反应模式的发展。4η3-烯丙基炔的偶联反应通过乙烯基烯烃中间体进行，通常通过与单炔反应提供开链η5-戊二烯络合物5(路径a)或η5-环戊二烯络合物6(路径b)(方案1)。还报道了两个炔烃的结合，导致了η1，η4-甲基环己二烯络合物的形成(路径c)。7通过控制双炔反应中决定环大小的迁移插入的区域化学，我们最近建立了第一个烯丙基/炔环加成反应，以获得高选择性的七元环体系(路径d)。8，9为了开发这种反应模式的合成潜力，人们寻求价格更低、反应活性更高的有机金属体系来开发有机方法。在这篇通讯中，我们报道了不饱和的全甲基环戊二烯基钴(III)与炔类化合物通过金属介导的分子间[3+2+2]环加成反应生成取代的η5-环庚二烯基络合物。随后的亲核烷基化/解离过程以高度区域选择性和立体选择性的方式提供了功能化的有机环庚二烯，为构建具有合成价值的七元环体系提供了收敛的新方法。
Transition metal-mediated cycloaddition reactions provide synthetic access to important organic ring systems inaccessible by traditional cycloaddition methodology. 2 Seven-membered-ring synthesis is prominent among these efforts, with important recent advances in two-component cycloadditions and intramolecular cyclization methodology. 3 Our investigation is focused on the development of metal-mediated allyl/alkyne cycloaddition reactivity patterns, targeting intermolecular three-component cyclization processes. 4 η3-Allyl alkyne coupling reactions proceed via vinyl olefin intermediates and typically provide open-chain η5-pentadienyl complexes5 (path a) or η5-cyclopentadienyl complexes6 (path b) from reaction with a single alkyne (Scheme 1). Incorporation of two alkynes has also been reported, leading to the formation of η1, η4-methanocyclohexadiene complexes (path c). 7 By controlling the regiochemistry of the migratory insertion that determines ring size in the double alkyne reactions, we recently established the first allyl/alkyne cycloaddition reactions to yield seven-membered-ring systems with high selectivity (path d). 8, 9 To exploit the synthetic potential of that iridium-mediated reactivity pattern, less expensive and more reactive organometallic systems were sought for the development of organic methodology.In this communication, we report that unsaturated permethylcyclopentadienylcobalt (III) allyl complexes react with alkynes to give substituted η5-cycloheptadienyl complexes by metal-mediated intermolecular [3+ 2+ 2] cycloaddition. Subsequent nucleophilic alkylation/decomplexation procedures provide functionalized organic cycloheptadienes in a highly regioselective and stereoselective manner, providing convergent new methodology for the construction of synthetically valuable seven-memberedring systems.