Alkyl groups, Wagner-Meerwein rearrangement

Skeletal rearrangements of carbenium ion species 2, that involve nucleophilic 1,2-migrations of alkyl groups, are called Wagner-Meerwein rearrangements... 

Alkyl groups can also migrate to a carbocation centre in Wagner-Meerwein rearrangements (or shifts). 

C2 symmetry), a high-symmetry chiral cage-shaped tricyclic hydrocarbon closely related to D2 twistane. Wagner-Meerwein rearrangement (144) of the unsaturated carboxylic acid (-)-151 provided the lactone (-)-168, which in turn was converted into the ketone (+)-170 via a series of intermediates, including the mesylate 169 whose intramolecular alkylation was a crucial step in this approach. Removal of the carbonyl group by Wolff-Kishner reduction completed the synthesis of (+)-brexane (171) (145). 

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