Metal-halogen exchange-initiated intramolecular conjugate addition reactions of conjugated acetylenic esters
摘要:
The lithium-iodine exchange-initiated intramolecular conjugate addition reactions of some model gamma-iodo-alpha,beta-acetylenic esters have been examined. Product mixtures arising from proton abstraction reactions were observed in reactions leading to 5-membered ring formation. More efficient cyclizations resulted when reactions were conducted in the presence of trimethylsilyl chloride to trap intermediate allenolate ions. Allenolate ion trapping by an internal electrophilic center in 26 resulted in the highly efficient formation of bicyclic ester 27.
Platinum-Catalyzed Hydrosilylations of Internal Alkynes: Harnessing Substituent Effects to Achieve High Regioselectivity
作者:Douglas A. Rooke、Eric M. Ferreira
DOI:10.1002/anie.201108714
日期:2012.3.26
Rule of thumb: The high yielding title reaction is described with a focus on understanding the factors that govern the regioselectivity of the process (see scheme). Electronic, steric, and functional group properties all influence the selectivity, an understanding of which allows the selective formation of trisubstituted vinylsilanes, which are synthetically useful compounds for accessing stereodefined
Gold‐Catalyzed [4+2] Annulation/Cyclization Cascades of Benzisoxazoles with Propiolate Derivatives to Access Highly Oxygenated Tetrahydroquinolines
作者:Rajkumar Lalji Sahani、Rai‐Shung Liu
DOI:10.1002/anie.201707423
日期:2017.10.2
Tag team: This work describes gold-catalyzed [4+2] annulation/cyclizationcascades of electron-deficient alkynes with benzisoxazoles to yield quinoline oxides chemoselectively. With the same reactants, a new relay catalysis using gold and zinc(II) catalysts afford highly oxygenated tetrahydroquinoline derivatives stereoselectively. Tf=trifluoromethanesulfonyl.
Gold-catalyzed formal [4π+2π]-cycloadditions of tert-butyl propiolates with aldehydes and ketones to form 4H-1,3-dioxine derivatives
作者:Somnath Narayan Karad、Wei-Kang Chung、Rai-Shung Liu
DOI:10.1039/c5cc04538j
日期:——
Novel gold-catalyzed [4π+2π]-cycloadditions of tert-butyl propiolates with aldehydes and ketones have been developed to form 4H-1,3-dioxine derivatives.
An analysis of the influences dictating regioselectivity in platinum-catalyzed hydrosilylations of internal alkynes
作者:Douglas A. Rooke、Zachary A. Menard、Eric M. Ferreira
DOI:10.1016/j.tet.2014.03.012
日期:2014.7
A full account of our studies on internal alkyne hydrosilylations using platinum catalysis is described. We demonstrate that these transformations are highly governed by the electronic characteristics of the alkyne substituents, wherein the hydride will add preferentially to the more electron-deficient alkyne carbon. The steric and coordinative capabilities of the substituents influence the selectivity
完整介绍了我们对使用铂催化的内部炔烃氢甲硅烷基化的研究。我们证明,这些转变高度受炔烃取代基的电子特性支配,其中氢化物将优先添加至电子欠缺的炔烃碳上。取代基的空间和配位能力对选择性的影响程度要小得多,其中丙炔醇是唯一的例外。硅烷的选择在某些情况下是相关的。特定的硅烷将提供较高的区域选择性,而其他的则选择性要低得多。最终,使用13 C NMR化学位移数据可以完全预测加成的区域选择性,从而将这种反应性纳入目标反应设计中。
Gold-Catalyzed Michael-Type Reactions and [4 + 2]-Annulations between Propiolates and 1,2-Benzisoxazoles with Ester-Directed Chemoselectivity
作者:Yashwant Bhaskar Pandit、Rajkumar Lalji Sahani、Rai-Shung Liu
DOI:10.1021/acs.orglett.8b02663
日期:2018.11.2
This work reports gold-catalyzed reactions between 1,2-benzisoxazoles and propiolate derivatives with ester-controlled chemoselectivity. For ethyl propiolates 1′, their gold-catalyzed reactions afforded Michael-type products 4, whereas tert-butyl propiolates 1 preferably underwent [4 + 2]-annulations, further yielding 6H-1,3-oxazin-6-one derivatives 3.
这项工作报告了1,2-苯并恶唑与丙酸酯衍生物之间的金催化反应,并具有酯控制的化学选择性。对于丙酸乙酯1',其金催化的反应得到迈克尔型产物4,而丙酸叔丁酯1优选经历[4 + 2]环化,进一步产生6 H -1,3-恶嗪-6-一衍生物3。