[3 + 4] Annulation of α,β-Unsaturated Acylsilanes with Enolates of α,β-Unsaturated Methyl Ketones: Scope and Mechanism
[3 + 4] Annulation of α,β-Unsaturated Acylsilanes with Enolates of α,β-Unsaturated Methyl Ketones: Scope and Mechanism
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DOI：
10.1021/ja980022
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发表时间：
1998-05
影响因子：
15
通讯作者：
K. Takeda;A. Nakajima;M. Takeda;Y. Okamoto;Taku Sato;E. Yoshii;and Toru Koizumi;M. Shiro
中科院分区：
文献类型：
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作者：
K. Takeda;A. Nakajima;M. Takeda;Y. Okamoto;Taku Sato;E. Yoshii;and Toru Koizumi;M. Shiro
(β-(三甲基甲硅烷基)丙烯酰基)(叔丁基)二甲基硅烷的E和Z异构体与α,β-不饱和甲基酮的烯醇锂在-80至-30℃下反应，分别得到顺式5,6-和反式5,6-二取代的3-环庚烯酮。在(β-(三正丁基甲锡烷基)丙烯酰基)硅烷的反应中观察到相同的[3 + 4]环化。通过NBS或mCPBA处理，成环产物很容易转化为4-环庚烯-1,3-二酮。观察到的成环立体特异性可以通过反应途径来解释，该反应途径涉及通过烯醇锂的 1,2-加合物的布鲁克重排生成的 1,2-二乙烯基环丙二醇中间体的阴离子氧基-Cope 重排。从(β-(三正丁基甲锡烷基)丙烯酰基)硅烷与2’-溴苯乙酮烯醇锂反应中分离出乙烯基环丙醇衍生物，并用LDA将其转化为环庚烯酮衍生物，为所提出的机理提供了强有力的支持。 1,2...的反应得到了进一步的支持。
Reactions of the E and Z isomers of (β-(trimethylsilyl)acryloyl)(tert-butyl)dimethylsilanes with lithium enolate of α,β-unsaturated methyl ketones at −80 to −30 °C afford cis-5,6- and trans-5,6-disubstituted 3-cyclohepetenones, respectively. The same [3 + 4] annulation is observed in the reaction of (β-(tri-n-butylstannyl)acryloyl)silanes. The annulation products are readily transformed into 4-cycloheptene-1,3-dione by treatment with NBS or mCPBA. The observed stereospecificity in the annulation is explained by the reaction pathway that involves an anionic oxy-Cope rearrangement of 1,2-divinylcyclopropanediol intermediate generated via Brook rearrangement of the 1,2-adduct of a lithium enolate. Isolation of vinylcyclopropanol derivative from the reaction of (β-(tri-n-butylstannyl)acryloyl)silanes with lithium enolate of 2‘-bromoacetophenone and its transformation into cycloheptenone derivative with LDA provide strong support for the proposed mechanism. Further support is obtained from the reactions of 1,2...