39795-59-0Relevant academic research and scientific papers
Direct ortho-Arylation of Pyridinecarboxylic Acids: Overcoming the Deactivating Effect of sp2-Nitrogen
Johnston, Adam J. S.,Ling, Kenneth B.,Sale, David,Lebrasseur, Nathalie,Larrosa, Igor
supporting information, p. 6094 - 6097 (2016/12/09)
Direct arylations of pyridines are challenging transformations due to the high Lewis basicity of the sp2-nitrogen. The use of carboxylates as directing groups is reported, facilitating the Pd-catalyzed C-H arylation of this difficult class of substrates. This methodology allows regioselective C3/C4 arylation, without the need to use solvent quantities of the pyridine, and using low-cost chloro- and bromoarenes as coupling partners. Furthermore, carboxylates could be employed as traceless directing groups through a one-pot C-H arylation/Cu(I)-mediated decarboxylation sequence, thereby accessing directing-group-free pyridine biaryls.
Phase-Transfer-Catalyzed Gomberg-Bachmann Synthesis of Unsymmetrical Biarenes: A Survey of Catalysts and Substrates
Beadle, James R.,Korzeniowsky, Stephen H.,Rosenberg, David E.,Garcia-Slanga, Blanche J.,Gokel, George W.
, p. 1594 - 1603 (2007/10/02)
Two problems have hindered the Gomberg-Bachmann (GB) and Pschorr reactions of arenediazonium cations: the instability of the arenediazonium salts and side reactions.Arenediazonium tetrafluoroborate and hexafluorophosphate salts can be prepared in high yield and purity and can be stored safely.Unfortunately, these salts are insoluble in most nonpolar organic solvents.Crown ether complexation or other phase-transfer (pt) catalytic methodology can ameliorate this situation, and reactions conducted by the approaches outlined herein often afforded coupling or cyclization products in high yield and corresponding purity.The use of crown ethers, quarternary 'onium salts, lipophilic carboxylic acid salts, and even the polar cosolvent acetonitrile increase the utility of the ptGB reaction dramatically.Sixty examples of couplings are reported along with an assessment of selectivities.A number of examples are also presented of phase-transfer-type Pschorr cyclizations.In the latter case, the use of potassium superoxide, KO2, is introduced to suppress indazole formation.
Quantitative Determination of the Electronic Effects of Pyridyl Groups
Shkurko, O. P.,Baram, S. G.,Mamaev, V. P.
, p. 60 - 65 (2007/10/02)
The series of ? constants of 2-, 3-, and 4-pyridyl groups was calculated on the basis of data from the 1H, 13C, and 19F NMR spectra of isomeric aminophenyl-, phenyl-, and fluorophenylpyridines.The literature ? constants and the values found in the research were analyzed.
