Rearrangements charge-accelerated

A nonconcerted mechanism of the 3-aza-Cope rearrangement of the enammonium salts has also been proposed by Mariano and coworkers 116a,ft, although the charge-accelerated rearrangements so far discussed proceed via the pericyclic route. The zwitterionic 7V-vinylisoquinuclidines formed from substrates 173 and a propiolate ester rearrange to fused heterocyclic compounds 174 through a stepwise pathway (Scheme... 

Isomerization of phenols 137 over sUica gel in the solid phase furnishes the corresponding 2,3-dihydro-4-oxo-4//-l-benzopyrane derivatives 138 (equation 60) ° . The cascades of the charge-accelerated rearrangements of the ortl o-(l,l-dimethylpropenyl)phenol 139 catalyzed by Bronsted acid (e.g. trifluoroacetic acid, equation 61) as well as by Lewis acids (anhydrous AICI3 or TiCLj, equations 62 and 63) proceed via the common intermediate 140 . 

---