Sodium hydrogen sulfide, reaction with rearrangement

In the presence of base, 2-isocyanoalkanenilriles [70] react with alcohols, thiols or hydrogen sulfide to form imidazoles which have oxygen or sulfur groups in the 4(5) position. The reactions appear to proceed via the 4ff-imidazoles, which rearrange to the Iff-isomers [71]. There are similarities to the synthesis of 4-methoxyimidazole made, in 60% yield, by refluxing the Af-cyanomethylimino ester of formic acid with sodium methoxide in methanol [72]. 

Oxidation of the heterocycles with common reagents such as MCPBA, sodium periodate or hydrogen peroxide cleanly affords the sulfoxides and sulfones, and it is clear that the sulfur atom is the principal centre of reaction for electrophiles. While the sulfone is a quite inert functionality, the sulfoxides may be reduced to the sulfides with phosphorus pen-tasulfide as for the tetrahydro systems (78CJC1423). Positive halogen sources likewise react at sulfur, and the intermediate sulfonium halide rearranges, usually by 1,2-shift to the a-halo product. 

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