A Comparison of Catalysts to Promote Imidazolide Couplings Including the Identification of 2-Hydroxy-5-nitropyridine as a New, Safe, and Effective Catalyst
摘要:
Five catalysts were compared with respect to their safety and catalytic effectiveness for promoting imidazolide couplings, Reaction rate enhancement, shock sensitivity, and differential scanning calorimetry (DSC) data were considered in this analysis. 6-Chloro-1-hydroxybenzotriazole, which has been described in the literature as a safe catalyst, was found to be shock sensitive. 2-Hydroxy-5-nitropyridine is a new catalyst for this type of reaction and was found to be safe, effective, readily available, and similar in price to that of the 1-hydroxybenzotriazole, a common catalyst for promoting acylation reactions.
Rhodium-Catalyzed Oxidative Amidation of Sterically Hindered Aldehydes and Alcohols
作者:Trang T. Nguyen、Kami L. Hull
DOI:10.1021/acscatal.6b02541
日期:2016.12.2
has been developed with sterically hindered aldehydes and alcohols for the synthesis of amides containing a quaternary carbon at the α position. A variety of amine nucleophiles, both aliphatic and aromatic, are employed and afford the corresponding amides in good to excellent yields. Finally, mechanistic studies are performed to gain insight into both catalytic cycles.
TCFH–NMI: Direct Access to <i>N</i>-Acyl Imidazoliums for Challenging Amide Bond Formations
作者:Gregory L. Beutner、Ian S. Young、Merrill L. Davies、Matthew R. Hickey、Hyunsoo Park、Jason M. Stevens、Qingmei Ye
DOI:10.1021/acs.orglett.8b01591
日期:2018.7.20
Challenging couplings of hindered carboxylic acids with non-nucleophilic amines to form amide bonds can be accomplished in high yields, and in many cases, with complete retention of the adjacent stereogenic centers using the combination of N,N,N′,N′-tetramethylchloroformamidinium hexafluorophosphate (TCFH) and N-methylimidazole (NMI). This method allows for in situ generation of highly reactive acyl imidazolium
Functionalization of α‐C(sp
<sup>3</sup>
)−H Bonds in Amides Using Radical Translocating Arylating Groups
作者:Niklas Radhoff、Armido Studer
DOI:10.1002/anie.202013275
日期:2021.2.15
α‐C−H arylation of N‐alkylamides using 2‐iodoarylsulfonyl radical translocating arylating (RTA) groups is reported. The method allows the construction of α‐quaternary carbon centers in amides. Various mono‐ and disubstituted RTA‐groups are applied to the arylation of primary, secondary, and tertiary α‐C(sp3)−H‐bonds. These radical transformations proceed in good to excellent yields and the cascades
A highly efficient intramolecular selective aryl migration/desulfonylation of 2-bromo-N-aryl-N-(arenesulfonyl)amide via visiblelight-inducedphotoredoxcatalysis has been accomplished. This approach allows for the construction of a variety of multisubstituted N,2-diarylacetamide under mild reaction conditions.
chromium-catalyzed activation of acyl C–O bonds with magnesium for amidation of esters with nitroarenes. Low-cost chromium(III) chloride shows high reactivity in promoting amidation by using magnesium as reductant and chlorotrimethylsilane as additive. It provides a step-economic strategy to the synthesis of centrally important amide motifs using inexpensive and air-stable nitroarenes as amino sources.