Isatogens nucleophilic addition

The nitrone group of the isatogen ring functions as a 1,3-dipolar system and takes part in a number of cycloaddition reactions with substituted olefins and acetylenes. The resulting adducts, in most cases, are not easily isolated and undergo further reactions, particularly nucleophilic addition and/or ring expansion, to give a variety of products. 

Isatogens, last reviewed in 1954,5 are usually represented as 1, but they are more fully described by the additional canonical structures 5-7. The addition of nucleophiles and some dipolarophiles is indicated by 5... 

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