Synthesis of new organic compounds possessing biological activity is very challenging and is a current trend in medicinal chemistry. In recent studies benzofuroxan derivatives have been described as drugs active against bacteria and fungi, based on the ability of these compounds to induce intracellular release of nitric oxide (II). Consequently, many substances arising from reactions between(di)сhloro(di)nitrobenzofuroxans and different aliphatic, aromatic amines, amino acids, aminoalcohol nitrates, sulfanilamides, polyene antibiotics and other nucleophiles have been prepared. Novel 2H-benzimidazole 1,3-dioxides were also obtained by interaction of benzofuroxans with alcohols in sulfuric or perchloric acids. We also proposed a new method for the preparation of 2H-benzimidazole 1,3-dioxides by reaction of o-benzoquinonedioxime with ketones. Further nitration of the obtained compounds yielded a wide range of Sepin-1 analogues (separase inhibitors) with various substituents in the 2-position.
Beside their high biological activity, 2H-benzimidazole 1,3-dioxides can be involved into thermal reactions. Heating of 2Н-benzimidazole 1,3-dioxides resulted in the formation of 3Н-[2,1,4]benzoxadiazine 4-oxides, which are unstable and easily transformed into initial 2H-benzimidazole 1,3-dioxides on exposure to sunlight. More prolonged heating of 3Н-[2,1,4]benzoxadiazine 4-oxides caused sequential elimination of the N-oxide oxygen atom to form 2H-benzimidazole mono N- oxides as final products of thermal reactions at moderate temperatures.