Lewis Base-Promoted Ring-Opening 1,3-Dioxygenation of Unactivated Cyclopropanes Using a Hypervalent Iodine Reagent
作者:Matthew H. Gieuw、Zhihai Ke、Ying-Yeung Yeung
DOI:10.1002/anie.201713422
日期:2018.3.26
A facile and effective system has been developed for the regio‐ and chemoselective ring‐opening/electrophilic functionalization of cyclopropanes through C−C bond activation by [bis(trifluoroacetoxy)iodo]benzene with the aid of the Lewis basic promoter p‐toluenesulfonamide. The p‐toluenesulfonamide‐promoted system works well for a wide range of cyclopropanes, resulting in the formation of 1,3‐diol products
(up to 95%, 86% ee) but also a concomitant oxidative kinetic resolution of the alcohol substrates (S > 20). In the case of bishomoallylic alcohols, an intriguing ligand-induceddivergentreactivity was observed. A terminal-to-internal alkene isomerization promoted by Rh/L7 followed by redox isomerization using Rh/BINAP system produced chiral ketones bearing a γ-stereocenter with high yield and enantioselectivity
Organolanthanide catalyzed hydrogenation and hydrosilylation of substituted methylenecycloalkanes
作者:Gary A. Molander、Jo¨rn Winterfeld
DOI:10.1016/s0022-328x(96)06276-6
日期:1996.11
This communication presents a study of the scope of the catalytic hydrogenation and hydrosilylation of chiral exomethylene-substituted cyclopentanes and cyclohexanes utilizing the organolanthanide precatalysts Cp2 LnCH(SiMe3)2 (CpC5Me5; LnSm, Yb). Both reaction types are sterically driven and lead to thecis-diastereomer as the major product. Additionally, the hydrosilylation is regiospecific, the silane
该交流介绍了利用有机镧系元素预催化剂Cp 2 LnCH(SiMe 3)2(CpC 5 Me 5 ; LnSm,Yb)对手性异亚甲基取代的环戊烷和环己烷进行催化加氢和硅氢加成反应的范围的研究。两种反应类型都是空间驱动的,并导致以顺式-非对映异构体为主要产物。另外,氢化硅烷化是区域特异性的,硅烷仅位于双键的末端位置。
Carbonyl methylenation of easily enolizable ketones
conformational equilibria of the titled compounds, 10–13, have been determined by 1HNMR and analysed in terms of steric (A(1,3) repulsion, 15) and electronic effects. The conformational equilibria of OMe and Br derivatives depend on the position and electronic properties of ω-substituent/s, attached to the doublebond, which may be rationalized in terms of “anomeric” type of resonance, 9. In contrast