Wagner-Meerwein migration

Various mechanisms are discussed for the migration of a benzyl group including, e.g., a two-stage Cope or reverse Claisen rearrangement as well as a preference of direct [l,5]-shift over successive Wagner-Meerwein migrations (equation 115)173. 

Reaction intermediates formed in the nitration of a series of a,/i-unsaturatcd esters, such as (47), with N02BF4 have been reported to exhibit the expected behaviour of a-carbonyl cations. Three diagnostic reaction types were observed (1) Ritter reaction (2) cyclopropane formation from propyl cations (3) Wagner-Meerwein migration of alkyl groups. Semi-empirical calculations of the relative gas-phase stabilities of the proposed intermediate cations have also been performed.53... 

Wagner-Meerwein migrations within a cyclopropylcarbinyl cation (Figure 57). However there is another interesting fact about these reactions that led Roberts to suggest an alternative possibility solvolysis of cyclopropylcarbinyl tosylate is about a million times faster than that of its nearest acyclic analog, isobutyl tosylate suggesting that the cation... 

Pachuau, Z., Lyngdoh, R. H. D. Moiecuiar orbitai studies on the Wagner-Meerwein migration in some acyclic pinacol-pinacolone rearrangements. J. Chem. Sci. (Bangalore, India) 2004, 116, 83-91. 

The outcome of solvolysis of a sulphonic ester of a 19-hydroxy-steroid apparently depends upon functional groups in rings a and b. The 19-tosylates (501 3/3-OAc, 5a or SP-3-oxo) react by Wagner-Meerwein migration of C-1, giving the... 

The manner in which the extensively studied fenchyl carbocation rearranges is also highly sensitive to attached functionality as demonstrated in studies of the effects of a 2-aryl substituent at C(2) of the fenchyl system. In a study conducted by Starling, it was found that ort/ o-substituted aryl groups inhibited Wagner-Meerwein migration except when substituted with... 

The next step for the reader is to formulate the sequence of Wagner-Meerwein migrations starting from C8 and C9 labeled cations 17 to confirm that the scrambling of deuterium corresponds with the data experimentally observed. 

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

Addition of bromine to 1 in chloroform solution at 10°C led in high yield to the formation of the exo-5-a/ih -7-dibromide 2. No other products were isolated. The formation of this rearranged product can be explained in terms of Wagner-Meerwein rearrangement where migration of the aryl group is involved (eqn. 1). 

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