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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Benzylic activation and stereocontrol in tricarbonyl(arene)chromium complexes ： ウィキペディア英語版 Benzylic activation and stereocontrol in tricarbonyl(arene)chromium complexes Benzylic activation and stereocontrol in tricarbonyl(arene)chromium complexes refers to the enhanced rates and stereoselectivities of reactions at the benzylic position of aromatic rings complexed to chromium(0) relative to uncomplexed arenes. Complexation of an aromatic ring to chromium stabilizes both anions and cations at the benzylic position and provides a steric blocking element for diastereoselective functionalization of the benzylic position. A large number of stereoselective methods for benzylic and homobenzylic functionalization have been developed based on this property.〔Uemura, M. ''Org. React.'' 2006, ''67'', 217. 〕 ==Introduction== The reaction between tricarbonylchromium complexes Cr(CO)3L3 and electron-rich or electron-neutral aromatic rings produces tricarbonyl(arene)chromium complexes (arene)Cr(CO)3.〔Mahaffy, C. A. L.; Pauson, P. ''Inorg. Synth.'' 1990, ''28'', 137.〕 Complexation to chromium(0) activates the side chain of the arene, facilitating dissociation of a benzylic proton or leaving group or nucleophilic addition to the homobenzylic position of styrenes. Further transformations of the resulting conformationally restricted, benzylic anion or cation involve the approach of reagents ''exo'' to the chromium fragment. Thus, benzylic functionalization reactions of planar chiral chromium arene complexes are highly diastereoselective. Additionally, the chromium tri(carbonyl) fragment can be used as a blocking element in addition reactions to ''ortho''-substituted aromatic aldehydes and alkenes. An ''ortho'' substituent is necessary in these reactions to restrict conformations available to the aldehyde or alkene.〔 Removal of the chromium fragment to afford the metal-free functionalized aromatic compound is possible photolytically〔 or with an oxidant.〔 ''(1)''File:CrAreneGen.png 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Benzylic activation and stereocontrol in tricarbonyl(arene)chromium complexes」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.