Biaryl formation using the suzuki protocol: Considerations of base, halide, and protecting group.
摘要:
The generation of aryl anions prior to quenching with a trialkyl borate has been shown to be sensitive to the composition of the aryl substrate. Aryl iodides containing remote benzyl ether substituents undergo trans-metallation with sec-BuLi to cleanly give the desired aryl anions whereas the corresponding bromides afford appreciable quantities of dianionic intermediates. The arylboronic acids derived from alkylation of these anions subsequently undergo a palladium mediated coupling with aryl halides to provide good yields of the desired biaryls. Copyright (C) 1996 Elsevier Science Ltd.
Stepwise Mechanism for the Bromination of Arenes by a Hypervalent Iodine Reagent
作者:Albert Granados、Alexandr Shafir、Ana Arrieta、Fernando P. Cossío、Adelina Vallribera
DOI:10.1021/acs.joc.9b02784
日期:2020.2.21
A mild, metal-free bromination method of arenes has been developed using the combination of bis(trifluoroacetoxy)iodobencene and trimethylsilyl bromide. In situ-formed dibromo(phenyl)-λ3-iodane (PhIBr2) is proposed as the reactive intermediate. This methodology using PIFA/TMSBr has been applied with success to a great number of substrates (25 examples). The treatment of mono-substituted activated arenes
In a convergent approach, an advanced intermediate (2) in a projected totalsynthesis of the alkaloid (-)-lemonomycin (1) was prepared from readily available starting materials. The key transformations were a Pictet-Spengler cyclization, a Strecker-type amino alkylation, and an N-acyliminium cyclization.
Electrophilicaromaticbromination is the most common synthetic method used to prepare aryl bromides, which are very useful intermediates in organic synthesis. To understand the experimental results in electrophilicaromaticbrominations, ab initio calculations are used here for a tentative analysis of the positional selectivity. The calculated results agree well with the corresponding experimental
Asymmetric Total Syntheses of (−)-Renieramycin M and G and (−)-Jorumycin Using Aziridine as a Lynchpin
作者:Yan-Chao Wu、Jieping Zhu
DOI:10.1021/ol9024919
日期:2009.12.3
By exploring the triple reactivity of two aziridines and double nucleophilicity of two aromatics, convergent and versatile syntheses of the above four natural products were developed.
An Efficient Synthetic Approach to Cyanocycline A and Bioxalomycin β2 via [C+NC+CC] Coupling
作者:H. Ümit Kaniskan、Philip Garner
DOI:10.1021/ja077853c
日期:2007.12.1
The Ag-I catalyzed [C+NC+CC] coupling reaction of a 2,3-bisaminoaldehyde 5, L-glycyl sultam 6, and methyl acrylate provides highly functionalized pyrrolidine 7, the key intermediate in an efficient synthetic approach to the cyanocycline and bioxalomycin families of natural products. This powerful multicomponent reaction-based strategy reduces the number of steps needed to make these complex targets by more than one-third and paves the way for biological and biochemical evaluation of this natural product family.