Aromatic halogenations, sodium periodate

The sodium periodate-mediated oxidation of alkali halides is a useful method to accomplish the halogenation of aromatic compounds. Accordingly, NaCl is successfully employed as a chlorine source for the chlorination of various aromatic compounds, although mixtures of regioisomers are sometimes obtained on the other hand, the related sodium periodate-mediated bromina-tion reaction, which uses lithium bromide or sodium bromide as halogen source, affords the expected brominated products in a regioselective fashion (eq 33). ... 

Some of the investigations carried out in the first half of the twentieth century were related to CL associated with thermal decomposition of aromatic cyclic peroxides [75, 76] and the extremely low-level ultraviolet emission produced in different reaction systems such as neutralization and redox reactions involving oxidants (permanganate, halogens, and chromic acid in combination with oxalates, glucose, or bisulfite) [77], In this period some papers appeared in which the bright luminescence emitted when alkali metals were exposed to oxygen was reported. The phenomenon was described for derivatives of zinc [78], boron [79], and sodium, potassium, and aluminum [80]. 

The only method which can be used for monocyclic aromatic 1,2,3-triazines as well as for condensed 1,2,3-triazines is the oxidation of iV-aminopyrazoles 1, vV-aminoindazoles 3, 7 or other condensed A-aminopyrazoles. The following reagents were used for the oxidation lead(IV) acetate, 7,77,82,104 110,116 lead(IV) oxide/trifluoroacetic acid,77 106 nickel peroxide,1- 1 77 manganese(IV) oxide,77 sodium and potassium periodate,78-103 halogenating agents,79-82,102 111 and electrooxidation.112 Sodium periodate78,103 seems to be the best reagent for monocyclic 1,2,3-triazines. 

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