Oxidation of N‐heterocyclics: A green approach

Abstract

Environmentally benign oxidation methods satisfy the postulates of green chemistry. Heterocyclic Noxides have applications in synthetic organic chemistry, chemotherapy and agrochemicals. Synthesis of Noxides using green oxidants will be attractive over the conventional methods. The presence of the N‐oxide group in the azine ring makes it more subject to electrophilic and nucleophilic attack and substantially expands the synthetic approaches for the modification of nitrogen‐containing heterocyclics. That is the reason for the increasing interest in the chemistry of heterocyclic N‐oxides. Some reactions adopted for oxidation of N‐heterocyclics have been discussed. Stereochemical and spectroscopic aspects have been mentioned. It will be advantageous if anchored catalysts are employed for industrial exploitation. Several physiochemical aspects of various methods have been discussed.

Intramolecular cyclization of β-nitroso-o-quinone methides. A theoretical endoscopy of a potentially useful innate ‘reclusive’ reaction

“…The N-O 2 bond in 10 or 9 falls within the range 1.202-1.242Å found in furoxans 74 and it remains as short as in the NO 2 group (Table 2), a feature common to heteroaromatic N-oxides. 75 The ring N-O 1 bond in 9 is quite stretched (ca. 1.492Å) and compares with the most strained bonds in fused furoxans.…”

Insights into the mechanistic and synthetic aspects of the Mo/P-catalyzed oxidation of N-heterocycles

“…11 There is, therefore, an unmet need for inexpensive and environmentally benign methods of azine and azole N -oxide synthesis based on readily available catalysts. 12 Herein, we report a combined mechanistic and synthetic study of the oxidation of a variety of azines and azoles catalyzed by molybdenum-phosphate catalysts with hydrogen peroxide as a terminal oxidant.…”