Deoxydative thiation of 3‐substituted pyridine N‐oxides with 4‐methoxytoluene‐α‐thiol: A divergent route to pyridinethiols

Abstract

Synthesis of 3‐substituted 2‐pyridinethiols was achieved by thiation of pyridine N‐oxides with 4‐methoxytoluene‐α‐thiol in the presence of diethylcarbamoyl chloride followed by cleavage of the resulting sulfides. The ease of substitution was shown to be affected by nucleophilicity of the N‐oxide oxygen. Addition of zinc bromide to the reaction, a need for triethylamine, decreased most of the yield for thiation products but the formation of 3‐methoxy‐2‐methoxybenzylthiopyridine was only improved. A plausible mechanism of the substitution, particularly β‐thiation to the N‐oxide function, is discussed compared with the regiochemistry observed in the reaction with diethoxyphosphoryl chloride instead of diethylcarbamoyl chloride. The debenzylation to pyridinethiol was also found to be dependent on the electron‐density in the pyridine ring.

Synthesis of Pyridine and Dihydropyridine Derivatives by Regio- and Stereoselective Addition toN-Activated Pyridines

“…The Sato group studied the addition of 4-methoxytoluene-α-thio when using diethylcarbamoyl chloride as an additional activating reagent for the pyridinium . In particular, the electronic effects of substituents at the 3-position of pyridine N -oxides were investigated.…”

Synthesis of Tetranuclear Rhodium and Iridium Complexes Directed by 6-Mercaptopyridin-2-ol: Electrochemical Behavior, Chemical Oxidation, and Coordination Chemistry

“…In addition, the IR spectrum showed several strong absorptions in the region 1650−1530 cm −1 that suggests the presence of this tautomer also in the solid state. Interestingly, the compounds 2-mercaptopyridin-3-ol and 3-mercaptopyridin-2-ol also exist mainly as the tautomers 3-hydroxy-2(1 H )-pyridinethione and 3-mercapto-2(1 H )-pyridone, respectively.…”