Carboxylic acids Wagner-Meerwein rearrangement

Electro-decarboxylation of endo-3-methoxycarbonyl-7-oxabicyclo[2.2. l]heptane-endo-2-carboxylic acid 20 in an MeOH—MeONa—(C) system gives exclusively an oxygen-assisted Wagner-Meerwein rearrangement via the intermediate carbenium ion forming 21 in 83% yield 54). Product 21 can be transformed to iridoid monoterp-enes 22 (Scheme 3-7)54a). 

A Wagner-Meerwein rearrangement via a bridged carbenium ion has been observed in the electrodecarboxylation of bicyclo[2.2.1]heptane-2-carboxylic acids (CXVIIa, CXVIIb, and CXVIIc), leading to the formation of the same products (CXVIII and CXIX) [Eq. (58)] [174]. This method has been successfully applied to synthesis of useful intermediates for natural product synthesis. Some examples are given in Eqs. (59) and (60) [175-179]. 

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). 

A Wagner-Meerwein-type rearrangement of the cation has been often observed in the oxidation of carboxylic acids (equation 59). The relative migratory aptitude of R and R has been studied, and this type of rearrangement has been applied to the synthesis of )-muscone (equation 60). ... 

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