Abstract
The photochemical isomerisation of hexatomic heterocyclic compounds has been discussed. The attention was focused on the mono- and dinitrogen hexatomic heterocycles. To justify the photochemical isomerisation of pyridines, Dewar isomers, azaprismane, and azaprefulvene derivatives have been proposed. The photoisomerisation of pyridinium salts requires a ring reduction with the formation of arizines. Pyridinium ylides gave photoisomerisation reaction through the formation of the corresponding azirines, while pyridinium N-oxide was required to react for the formation of the corresponding oxaziridines. The photochemical isomerisation of pyrazine derivatives, Dewar isomers, diazaprismane, and benzvalene intermediates has been proposed to justify the observed reactivity. Finally, in the case of pyridazine and pyrimidine derivatives, Dewar isomers were used to explain the obtained reaction products. In the discussion of the results, the presence of different mechanistic hypotheses has been evidenced.
Keywords: Pyridine, quinoline, isoquinoline, pyrazine, pyridazine, pyrimidine.
Graphical Abstract
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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