An Enantioselective Synthesis of 2-Aryl Cycloalkanones by Sc-Catalyzed Carbon Insertion
摘要:
Current methods for asymmetric alpha-arylation require blocking groups to prevent reaction at the alpha'-carbon, basic conditions that promote racemization, or multistep synthesis. This work records the first catalytic enantioselective examples of the diazoalkane-carbonyl homologation reaction. Medium ring 2-aryl ketones are prepared in one step in up to 98:2 er and 99% yield from the unsubstituted lower homologue by Sc-catalyzed aryldiazomethyl insertion with simple bis- and tris(oxazoline) ligands.
Carboxylation and Esterification of Functionalized Arylcopper Reagents
作者:Greg W. Ebert、Wayne L. Juda、Robert H. Kosakowski、Bing Ma、Liming Dong、Keith E. Cummings、Mwita V. B. Phelps、Adel E. Mostafa、Jianyuan Luo
DOI:10.1021/jo047731s
日期:2005.5.1
Functionalized arylcopper reagents have been produced in good yields at 25 °C from activated copper and the corresponding functionalized aryl iodides without the need of traditional organolithium or Grignard precursors. These organocopper compounds will undergo carboxylation with CO2 to form the corresponding copper benzoates. In turn, these salts can be acidified to produce the functionalized aryl
Domino Catalysis in the Direct Conversion of Carboxylic Acids to Esters
作者:I. Held、P. von den Hoff、D. S. Stephenson、H. Zipse
DOI:10.1002/adsc.200800268
日期:2008.8.4
The combined use of high concentration conditions, auxiliary bases, and new catalysts allows for the rapid synthesis of sterically hindered carboxylic acid esters at room temperature. Mechanistic analysis indicates the intermediate formation of acid anhydrides and subsequent rate-limiting transformation to the ester products.
Imidazolium salts have been effectively employed as suitable acyl transfer agents in amidation and esterification in organic synthesis. The weak acyl C(O)–C imidazolium bond was exploited to generate acyl electrophiles, which further react with amines and alcohols to afford amides and esters. The broad substrate scope of anilines and benzylic amines and base-promoted conditions are the benefits of
Titration of Nonstabilized Diazoalkane Solutions by Fluorine NMR
作者:Victor L. Rendina、Jason S. Kingsbury
DOI:10.1021/jo202214e
日期:2012.1.20
A new protocol for titrating nonstabilized diazoalkane solutions by quantitative 19F NMR is reported. An excess of 2-fluorobenzoic acid dissolved in CDCl3 is treated with the diazoalkane solution at a low temperature, immediately forming the corresponding 2-fluorobenzoate ester upon warming. A significant difference in the 19F chemical shift between the ester and acid is seen, allowing facile and accurate
报道了通过定量19 F NMR滴定不稳定的重氮烷溶液的新方案。用重氮烷溶液在低温下处理溶解在CDCl 3中的过量的2-氟苯甲酸,在加热后立即形成相应的2-氟苯甲酸酯。观察到酯和酸之间在19 F化学位移方面存在显着差异,从而可以轻松,准确地积分来确定滴度。该过程安全,快速,并且可以高精度指示活性重氮烷浓度。