期刊
JOURNAL OF ORGANIC CHEMISTRY
卷 79, 期 1, 页码 352-364出版社
AMER CHEMICAL SOC
DOI: 10.1021/jo402505f
关键词
-
资金
- MDS Research Foundation
- NSF CHE-1152491
The combination of experiments and computations reveals unusual features of stereoselective Rh(1)-catalyzed transformation of propargyl vinyl ethers into (E,Z)-dienals. The first step, the conversion of propargyl vinyl ethers into allene aldehydes, proceeds under homogeneous conditions via a cyclization-mediated mechanism initiated by Rh(I) coordination at the alkyne. This path agrees well with the small experimental effects of substituents on the carbinol carbon. The key feature revealed by the computational study is the stereoelectronic effect of the ligand arrangement at the catalytic center. The rearrangement barriers significantly decrease due to the greater transfer of electron density from the catalytic metal center to the CO ligand oriented trans to the alkyne. This effect increases electrophilicity of the metal and lowers the calculated barriers by 9.0 kcal/mol. Subsequent evolution of the catalyst leads to the in situ formation of Rh(I) nanoclusters that catalyze stereoselective tautomerization. The intermediacy of heterogeneous catalysis by nanoclusters was confirmed by mercury poisoning, temperature-dependent sigmoidal kinetic curves, and dynamic light scattering. The combination of experiments and computations suggests that the initially formed allene-aldehyde product assists in the transformation of a homogeneous catalyst (or a cocktail of catalysts) into nanoclusters, which in turn catalyze and control the stereochemistry of subsequent transformations.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据