Steric Effects in the Cycloaddition of Electron-Deficient 8,8-Dicyanoheptafulvene to Electron-Rich Unsymmetrically 6-Octylfulvene

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Title:	Steric Effects in the Cycloaddition of Electron-Deficient 8,8-Dicyanoheptafulvene to Electron-Rich Unsymmetrically 6-Octylfulvene 缺電子基取代之8,8-Dicyanoheptafulvene和給電子基不對稱取代之6-Octylfulvene的還化加成反應研究探討:立體效應影嚮性
Authors:	劉清揚于健良趙文芳
Contributors:	化學系
Keywords:	缺電子基電子基還化加成反應立體效應
Date:	1996-05
Issue Date:	2016-04-13 14:19:00 (UTC+8)
Abstract:	缺電子基雙取代之8,8-dicyanoheptafulvene (1a) 和給電子基不對稱單取乏之6-octylfulvence (2c)進行還化加成反應研究。探討fulvene的“環外取代基”（exocyclicsubstituents）對其進行還化加成反應之影響性。由實驗結果顯示，在所進行的[8+2]和[4+2]還化加成反應當中，fulvene皆傾向於經由遠離環外取代基立體障礙較大之環內雙鍵（endocyclic double bond）進行還化加成反應，顯示出極佳之位置選擇性（periselectivity）。在其進行[8+2]還化加成反應時，均顯示出完全地“反向”位向選擇性（anti regioselectivity）。但是，當其進行[4+2]還化加成反應時，卻顯示出相反地“同向”（syn）位向選擇性。在所有進行的反應當中，並未有分離出任何的[6+4]與[8+6]還化加成生成物。溫度效應為控制其還化加成反應之重要因素。 Thermal cycloaddition reaction of electron-dificient 8,8-dicyanheptafulvene(1a) with elector-rich unsymmetrically 6-substituted 6-octylfulvene (2c) has been invstigated to determine the effects of the fulvene exocyclic substituents on this cycloaddition. It has been found that the 6-substituent of the fulvene exert large influence on the periselectivity between the two endocyclic double bonds. The [8+2] and [4+2] cycloaddition reactions took place preferentially on the endocyclic double bond which is anti to the larger exocyclic sunstituent of the fulvene. The [8+2] and [4+2] cycloaddition reactions were found to proceed with exclusively anti regioseletivity and preferentially syn regioselectivity, respectively. In no cases were [6+4] and [ 8+6] cycloadducts obtained. The reaction shows a temperature dependency.
Relation:	華岡理科學報 13 民85.05 頁71-80
Appears in Collections:	[Department of Chemistry & Graduate Institute of Applied Chemistry ] journal articles

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