Nucleophilic substitution five-membered ring compounds

The formation of bicyclic intermediate (5) during the reaction suggested that the carbaphosphatrane framework is not maintened and one five-membered ring is cleaved by nucleophilic substitution. This different reactivity, in comparision to other /f-equatorial spirophosphoranes, could be best explained by the structural difference of compound (4). Because the hydrogen atom in (4) is fixed in an apical position, its acidity is lower than that of /f-equatorial spirophosphoranes. Therefore, nucleophilic substitution is thus preferred over deprotonation. 

Reissert compounds, 9, I 24, 187 Ring closure of ortlio-substituted t-anilines, heterocycles by, 14, 211 Ring-opening of flve-membered heteroaromatic anions, 41, 41 Ring synthesis of heteroaromatic nitro compounds, 25, 113 Ring transformations and cyclizations on reaction of azines with bifunctional nucleophiles, 43, 301 of five-membered heterocycles, 56, 49... 

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