Enantioselective Rh(II)-Catalyzed Desymmetric Cycloisomerization of Diynes: Constructing Furan-Fused Dihydropiperidines with an Alkyne-Substituted Aza-Quaternary Stereocenter
Described herein is an enantioselective dirhodium(II)-catalyzed cycloisomerization of diynes achieved by the strategy of desymmetrization, which not only represents a new cycloisomerization reaction of diynes but also constitutes the first Rh(II)-catalyzed asymmetricintramolecular cycloisomerization of 1,6-diynes. This protocol provides a range of valuable furan-fused dihydropiperidine derivatives
本文描述了一种通过去对称化策略实现的对映选择性二炔(II)催化的二炔环异构化,它不仅代表了一种新的二炔环异构化反应,而且构成了第一个 Rh(II)催化的 1,6- 不对称分子内环异构化。迪因斯。该协议提供了一系列有价值的呋喃稠合二氢哌啶衍生物,其具有对映异构体富集的炔基取代氮杂四元立体中心,具有高效、完全的原子经济性和出色的对映选择性(高达 98% ee)。此外,高度功能化的产品可以很容易地转化为各种合成有用的构建块,并与一系列药物分子结合。涉及协调 [3+2] 环加成 /[1, 通过 DFT 计算和机理研究阐明了 Rh(II) 类卡宾中间体的 2]-H 位移。更重要的是,获得了炔-二铑 (II) 的第一个单晶,表明 η涉及由二铑 (II) 对炔醛的2 -协调活化。发现了羧酸盐配体和炔醛之间的弱氢键,这可能使明确定义的桨状二铑 (II) 在催化这种转化方面与其他金属配合物不同。此外,对映选择性的起源由
New and Efficient Procedure for the Preparation of Unsymmetrical Silaketals
[reaction: see text] A new and efficient procedure for the preparation of unsymmetrical silaketals via a three-step protocol without isolation of the intermediates is presented. The unsymmetrical silyl ethers and silanes can also be readily obtained via this sequence of reactions.
In sharp contrast with the standard [2 + 2 + 2] cycloadditionreaction of diyne/ene, cobalt-mediated cycloadditions with γ-alkylidenebutenolide led to unprecedented cobalt(III) polycyclic complexes. A plausible mechanism supported by a computational study based on an unusual fragmentation of the butenolide moiety was postulated to account for this original reaction.
Efficient Construction of the Bicyclo[5.3.0]decenone Skeleton Based on the Rh(I)-Catalyzed Allenic Pauson−Khand Reaction
作者:Chisato Mukai、Izumi Nomura、Shinji Kitagaki
DOI:10.1021/jo020649h
日期:2003.2.1
3.0]deca-1,7-dien-9-one ring system by rhodium-catalyzed Pauson-Khandreaction (PKR) of allenynes with a sulfonyl group has been developed. Investigation of the rhodium-catalyzed PKR on 19 examples of 1,2-nonadien-8-yne derivatives demonstrated that (i) acceptable yields could be consistently achieved through the proper choice of the rhodium catalyst ([RhCl(CO)(2)](2) or [RhCl(CO)dppp](2)) depending
Cyano Diels−Alder and Cyano Ene Reactions. Applications in a Formal [2 + 2 + 2] Cycloaddition Strategy for the Synthesis of Pyridines
作者:Takeo Sakai、Rick L. Danheiser
DOI:10.1021/ja106901u
日期:2010.9.29
Two metal-free, formal [2 + 2 + 2] cycloaddition strategies for the construction of polycyclic pyridine derivatives are described that proceed via pericyclic cascade mechanisms featuring the participation of unactivated cyano groups as enophile and dienophile cycloaddition partners.