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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 Reactions of alkenyl- and alkynylaluminium compounds ： ウィキペディア英語版 Reactions of alkenyl- and alkynylaluminium compounds Reactions of alkenyl- and alkynylaluminium compounds involve the transfer of a nucleophilic alkenyl or alkynyl group attached to aluminium to an electrophilic atom. Stereospecific hydroalumination, carboalumination, and terminal alkyne metalation are useful methods for generation of the necessary alkenyl- and alkynylalanes.〔Zweifel, G.; Miller, J. A. ''Org. React.'' 1984, ''32'', 375. 〕 ==Introduction== Aluminium, like its congener boron, is less electronegative than carbon (Al, 1.61; C, 2.55); thus, aluminium-bound carbons in organoalanes possess partial negative charge and are nucleophilic as a result. Generally, however, organoalanes are not nucleophilic enough to transfer an organic group on their own (the exception being when carbonyl and enone acceptors are used, due to the high oxophilicity of aluminium〔Collins, P. W.; Dajani, E. Z.; Bruhn, M. S.; Brown, C. H.; Palmer, J. H.; Pappo, R. ''Tetrahedron Lett.'' 1975, 4217.〕). In most cases, nucleophilic activation of organoalanes is necessary for group transfer to take place. Like organoboranes, organoalanes possess an empty p orbital on the aluminium center that can receive electron density from an added nucleophile. The resulting negatively charged aluminate is much more nucleophilic than the neutral alane.〔Negishi, E.-i. ''J. Organometal. Chem. Lib.'' 1976, ''1'', 93.〕 This concept has been applied to methods for the synthesis of organic compounds from alkenyl- and alkynylalanes. The most notable applications are methods for the stereospecific synthesis of olefins. Alkenylalanes, which are easily synthesized with complete stereocontrol through alkyne hydroalumination, transfer the alkenyl unit to a variety of electrophiles. Alkynylalanes are less commonly used because alkali metal acetylides can be used for many of the same transformations as alkynylalanes. However, alkynylalanes are useful for the coupling of tertiary halides and alkynes (a reaction difficult to effect with alkali metal alkynes)〔Negishi, E.-i.; Baba, S. ''J. Am. Chem. Soc.'' 1975, ''97'', 7385.〕 and for conjugate addition〔Hooz, J.; Layton, R. B. ''J. Am. Chem. Soc.'' 1971, ''93'', 7320.〕 and epoxide opening reactions.〔Danishefsky, S.; Kitahara, T.; Tsai, M.; Dynak, J. ''J. Org. Chem.'' 1976, ''41'', 1669.〕 ''(1)''File:AlaneGen.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「Reactions of alkenyl- and alkynylaluminium compounds」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.