Dual Catalysis in Enantioselective Oxidopyrylium-Based [5 + 2] Cycloadditions
摘要:
A new method for effecting catalytic enantioselective intramolecular [5 + 2] cycloadditions based on oxidopyrylium intermediates is reported. The dual catalyst system consists of a chiral primary aminothiourea and a second achiral thiourea. Experimental evidence points to a new type of cooperative catalysis with each species being necessary to generate a reactive pyrylium ion pair that undergoes subsequent cycloaddition with high enantioselectivity.
Enantioselective Radical Construction of 5-Membered Cyclic Sulfonamides by Metalloradical C–H Amination
作者:Yang Hu、Kai Lang、Chaoqun Li、Joseph B. Gill、Isaac Kim、Hongjian Lu、Kimberly B. Fields、McKenzie Marshall、Qigan Cheng、Xin Cui、Lukasz Wojtas、X. Peter Zhang
DOI:10.1021/jacs.9b08894
日期:2019.11.13
azides can be effectively activated by the cobalt(II) complexes of D2-symmetric chiral amidoporphyrins for enantioselective radical 1,5-C-H amination to stereoselectively construct 5-membered cyclic sulfonamides. In addition to C-H bonds with varied electronic properties, the Co(II)-basedmetalloradical system features chemoselectiveamination of allylic C-H bonds and is compatible with heteroaryl groups
A Boron Alkylidene-Alkene Cycloaddition Reaction: Application to the Synthesis of Aphanamal
作者:Xun Liu、T. Maxwell Deaton、Fredrik Haeffner、James P. Morken
DOI:10.1002/anie.201705720
日期:2017.9.11
unusual net [2+2] cycloadditionreaction between boron alkylidenes and unactivated alkenes. This reaction provides a new method for the construction of carbocyclic ring systems bearing versatile organoboronic esters. Aside from surveying the scope of this reaction, we provide details about the mechanistic underpinnings of this process, and examine its application to the synthesis of the natural product
Ti-Catalyzed Multicomponent Oxidative Carboamination of Alkynes with Alkenes and Diazenes
作者:Zachary W. Davis-Gilbert、Letitia J. Yao、Ian A. Tonks
DOI:10.1021/jacs.6b09939
日期:2016.11.9
The inter- or intramolecular oxidative carboamination of alkynes catalyzed by [py2TiCl2NPh]2 is reported. These multicomponent reactions couple alkenes, alkynes and diazenes to form either α,β-unsaturated imines or α-(iminomethyl)cyclopropanes via a TiII/TiIV redox cycle. Each of these products is formed from a common azatitanacyclohexene intermediate that undergoes either β-H elimination or α,γ-coupling
Nickel-Catalyzed Allylic Substitution of Simple Alkenes
作者:Ryosuke Matsubara、Timothy F. Jamison
DOI:10.1002/asia.201000875
日期:2011.7.4
This report describes a nickel‐catalyzed allylic substitution process of simplealkenes whereby an important structural motif, a 1,4‐diene, was prepared. The key to success is the use of an appropriate nickel–phosphine complex and a stoichiometric amount of silyl triflate. Reactions of 1‐alkyl‐substituted alkenes consistently provided 1,1‐disubstituted alkenes with high selectivity. Insight into the
作者:John B. Feltenberger、Ryuji Hayashi、Yu Tang、Eric S. C. Babiash、Richard P. Hsung
DOI:10.1021/ol901434g
日期:2009.8.20
Benzyne-[2 + 2] cycloadditions with enamides are described. This effort led to the development of a highly stereoselectivetandem [2 + 2] cycloaddition−pericyclic ring-opening−intramolecular-N-tethered-[4 + 2] cycloaddition for rapid assembly of nitrogen heterocycles.