Pyridine W-oxide

Chemical/Physical. The gas-phase reaction of ozone with pyridine in synthetic air at 23 °C yielded a nitrated salt having the formula [CeHsNHJ NOs (Atkinson et al., 1987). Ozonation of pyridine in aqueous solutions at 25 °C was studied with and without the addition of ferf-butyl alcohol (20 mM) as a radical scavenger. With tert-hniyX alcohol, ozonation of pyridine yielded mainly pyridine W-oxide (80% yield), which was very stable towards ozone. Without terf-butyl alcohol, the heterocyclic ring is rapidly cleaved forming ammonia, nitrate, and the amidic compound W-formyl oxamic acid (Andreozzi et al., 1991). 

Figure 11.6. SHMO orbitals and orbital energies for (a) pyrrole (b) pyridine (c) pyridinium (d) pyridine-W-oxide (HOMO and LUMO only shown).

The gas-phase pyrolysis of 1-arylethyl acetates has also been used to determine o+ values of 0.81 and 0.016, respectively, for the 3- and 4-positions of pyridine W-oxide [75JCS(P2)277], These show that the 4-position is the most reactive, and little less reactive than that of a position in benzene further discussion is deferred to Section 9. 

According to Maselli235 6 is also formed when 1 is allowed to stand in a saturated solution of chlorine in water. Lately more complex reactions have been reported for 6. It reacts with pyridine W-oxide to give N-2-pyridyl saccharin264 presumably via an intermediate (97). 

The majority of studies involve aromatic N O ligands, some common examples being pyridine W-oxide and methyl substituted derivatives (I04-I06). They are versatile ligands,... 

Interactive mechanism for nucleophilic substitution on pyridine W-oxide... 

Substituted bipyridines were efficiently prepared by direct coupling between pyridine W-oxides and halopyridines using a palladium catalyst (Scheme 4) [20]. It is worth noting that pyridine W-oxides bearing electron-withdrawing substituents... 

Scheme 40 Reaction of pyridine W-oxide with benzyne...

Scheme 44 Reactions of pyridine W-oxides with cyclohexyl radical...

Scheme 45 Radical reaction of pyridine W-oxides with arylboronic acid...

A new approach for direct arylation of pyridine W-oxides with arylboronic acids through C-H functionalization has been developed (Scheme 45) [99]. This reaction can be performed at room temperature using catalytic silver (I) nitrate in the presence of potassium persulfate, thus giving 2-aryl derivatives of pyridine W-oxides. 

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