Benzimidazole 3- oxides, reaction with phosphorus oxychloride

Benzimidazole 3-oxides, e.g. (189), react with phosphorus oxychloride or sulfuryl chloride to form the corresponding 2-chlorobenzimidazoles. The reaction sequence involves first formation of a nucleophilic complex (190), then attack of chloride ions on the complex, followed by rearomatization involving loss of the fV-oxide oxygen (191 -> 192). 

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See also in sourсe #XX -- [ ]

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