Synthesis of N-oxides of pyridines and related compounds

Recent Literature

Sodium percarbonate is an ideal and efficient oxygen source for the oxidation of tertiary nitrogen compounds to N-oxides in excellent yields in the presence of various rhenium-based catalysts under mild reaction conditions.
S. L. Jain, J. K. Joseph, B. Sain, Synlett, 2006, 2661-2663.

The use of titanium silicalite (TS-1) in a packed-bed microreactor and H₂O₂ in methanol as solvent enable the formation of various pyridine N-oxides in very good yields. This flow process is a safer, greener, and more highly efficiency process than using a batch reactor. The device was used for over 800 hours of continuous operation while while the catalyst remained active.
S. Chen, S. Yang, H. Wang, Y. Niu, Z. Zhang, B. Qian, Synthesis, 2022, 54, 3999-4004.

Sodium perborate in acetic acid is an effective reagent for the oxidation of aromatic aldehydes to carboxylic acids, iodoarenes to (diacetoxyiodo)arenes, azines to N-oxides, and various sulphur heterocycles to S,S-dioxides. Nitriles undergo smooth oxidative hydration to amides when aqueous methanol is employed as solvent.
A. McKillop, D. Kemp, Tetrahedron, 1989, 45, 3299-3306.

Urea-hydrogen peroxide adduct (UHP) is stable, inexpensive and an easily handled reagent. UHP is used in an efficient solid state oxidation of different organic molecules: hydroxylated aldehydes and ketones (to hydroxylated phenols), sulfides (to sulfoxides and sulfones), nitriles (to amides) and nitrogen heterocycles (to N-oxides).
R. S. Varma, K. P. Naicker, Org. Lett., 1999, 1, 189-191.

Use of a solvent with greater density than the fluorous phase is an alternative to the U-tube method in phase-vanishing reactions in cases where both reactants are less dense than the fluorous phase.
N. K. Jana, J. G. Verkade, Org. Lett., 2003, 5, 3787-3790.