再次探讨了C 70 2–与有机卤化物的反应:2,5-(PhCH 2)2 C 70中非对映体亚甲基质子的异常磁当量
摘要:
C 70 2–与有机卤化物的反应产生了几种异构体产物。但是,异构体的结构尚未得到明确鉴定,即使该反应的第一份报告发表于十多年前,其反应仍然难以捉摸。在此,重新讨论了C 70 2–与ArCH 2 Br(Ar = Ph,o-,m-和p -BrC 6 H 4)的反应。两种类型的同分异构体的对位的2,5-和7,23-加合物(ARCH 2)2 Ç 70通过X射线单晶衍射,HRMS,1 H和13 C NMR以及UV-vis光谱学进行表征。在环境温度下记录的2,5-(PhCH 2)2 C 70的1 H NMR光谱中显示了C2非对位亚甲基质子的异常单峰共振而不是典型的AB四重共振。利用变温(VT)NMR和密度泛函理论(DFT)计算研究了意外的磁当量。结果表明,在C 70极性区域中较大的局部曲率可能是由2,5-(PhCH的C2非对映体亚甲基质子表现出的异常磁当量的原因2)2 C 70,表明在某些情况下,不可能像C
Ruthenium Porphyrin Catalyzed Intramolecular Carbenoid C−H Insertion. Stereoselective Synthesis of Cis-Disubstituted Oxygen and Nitrogen Heterocycles
作者:Wai-Hung Cheung、Shi-Long Zheng、Wing-Yiu Yu、Guo-Chuan Zhou、Chi-Ming Che
DOI:10.1021/ol034806q
日期:2003.7.1
[reaction: see text] A ruthenium porphyrin-catalyzed stereoselective intramolecularcarbenoid C[bond]H insertion is described. Using [Ru(II)(TTP)(CO)] as catalyst, aryl tosylhydrazones are converted to 2,3-dihydrobenzofurans, 2,3-dihydroindoles, and beta-lactams in good yields and remarkable cis selectivity (up to 99%). Enantioselective synthesis of 2,3-dihydrobenzofurans is also achieved with [Ru(II)(D(4)-Por*)(CO)]
rearrangement involving loss of methyl formate, 2π-electrocyclization of the resulting allylic cation, and elimination of the metal to regenerate the catalyst. Methoxymethyl ethers derived from 2-(dimethylphenylsilyl)cycloprop-1-enyl carbinols undergo gold-catalyzed rearrangement leading to [(Z)-(dimethylphenylsilyl)methylene]cyclopropanes in moderate to high yields with methyl formate as a byproduct. This
Generation of sulfur ylides by the desilylation of α-trimethylsilylbenzyl sulfonium salts
作者:Albert Padwa、John R. Gasdaska
DOI:10.1016/s0040-4020(01)86662-x
日期:1988.1
The [2,3]-sigmatropic rearrangement of sulfur ylides derived via the desilylation of several α-trimethylsilylbenzyl sulfonium salts has been studied. The initially formed ylide was found to rapidly equilibrate with the thermodynamically more stable ylide. In the absence of trapping reagents, a Sommelet-Hauser type rearrangement occurs.
.alpha.-Deuterium isotope effects in benzyl halides. 2. Reaction of nucleophiles with substituted benzyl bromides. Evidence for a change in transition-state structure with electron-donating substituents
作者:V. P. Vitullo、J. Grabowski、S. Sridharan
DOI:10.1021/ja00541a014
日期:1980.10
the following substrates and nucleophiles: p-methoxybenzyl bromide (Et/sub 3/N, SCN/sup -/, N/sub 3//sup -/, OH/sup -/, S/sub 2/O/sub 3//sup 2 -/), benzyl bromide (Et/sub 3/N, SCN/sup -/, N/sub 3//sup -/, OH/sup -/, S/sub 2/O/sub 3//sup 2 -/), and p-nitrobenzyl bromide (Et/sub 3/N, SCN/sup -/, N/sub 3//sup -/, S/sub 2/O/sub 3//sup 2 -/). In nearly all cases the second-order rate constant for each nucleophile