6311-86-0Relevant academic research and scientific papers
Synthetic Applications of N-N Linked Heterocycles. Part 14. The Preparation of α-(4-Pyridyl)esters and α-(4-Pyridyl)nitriles by Regiospecific Attack of Ester and Nitrile Anions on Pyridinium Salts
Sammes, Michael P.,Lee, Cheuk Man,Katritzky, Alan R.
, p. 2476 - 2482 (2007/10/02)
Reactions between N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium tetrafluoroborate (1) and lithio-derivatives of esters and nitriles give only low yields of 1,4-dihydro-adducts (3) and (7) due apparently to competing proton abstraction from the pyridone methyl groups.This limitation with salt (1) appears only with C-H acids of pKa > 20.Decomposition of the adducts under free-radical conditions yields α-(4-pyridyl)-esters (4) and -nitriles (8) essentially quantitatively.The same pyridyl-esters and -nitriles may be prepared conveniently in good overall yields by the reaction between the appropriate lithium salts and N-triphenylmethylpyridinium salts.The scope and limitations of the method are discucced. 2-Methyl-N-triphenylmethylpyridinium tetrafluoroborate is reported for the first time.
Synthetic Applications of N-N Linked Heterocycles. Part 8. Regiospecific Synthesis of 4-(α-Acylalkyl)pyridines by Attack of Lithium Enolates of Ketones γ to N-(2,6-Dimethyl-4-oxopyridin-1-yl)pyridinium Salts
Lee, Cheuk Man,Sammes, Michael P.,Katritzky, Alan R.
, p. 2458 - 2462 (2007/10/02)
The addition of N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium salts (2) - (4) to lithium enolates (1) of ketones in tetrahydrofuran at low temperatures gives regiospecifically high yields of 1,4-dihydro-adducts (5) - (7).These are readily isolated and can be decomposed under free-radical conditions, also in high yield, to 4-(α-acylalkyl)pyridines (8) - (10).Unsymmetrical dialkyl ketones give a mixture of two isomeric products, the ratio depending upon reaction conditions and steric factors. αβ-Unsaturated ketones, however, give products resulting from reaction exclusively at the position α' to the carbonyl group.
