Wagner-Meerwein type process

The Bamford-Stevens decomposition of tosylhydrazones by base has been applied to steroids, although not extensively. It has been demonstrated that the reaction proceeds via a diazo compound which undergoes rapid decomposition. The course of this decomposition depends upon the conditions in proton-donating solvents the reaction has the characteristics of a process involving carbonium ions, and olefins are formed, often accompanied by Wagner-Meerwein-type rearrangement. In aprotic solvents the diazo compound appears to give carbene intermediates which form olefins and insertion products ... 

The formation of sesquiterpenes by a carbocation mechanism means that there is considerable scope for rearrangements of the Wagner-Meerwein type. So far, only occasional hydride migrations have been invoked in rationalizing the examples considered. Obviously, fundamental skeletal rearrangements will broaden the range of natural sesquiterpenes even further. That such processes do occur has been proven beyond doubt by appropriate labelling experiments, and... 

Scheme 7.48. Two alternatives to account for methide migration.The first is a two-step process, where the leaving group departs in the first step and the methyl migrates in the second step. The alternative is a one-step process, where the methide shifts in concert with the leaving of the leaving group. The rearrangement is generally of the Wagner-Meerwein type.

The aconitine-type alkaloid (96) is most probably formed from the atisine skeleton through different modifications as indicated in Scheme 28.4. The intermediate 94 after a Wagner-Meerwein rearrangement process converts two fused six-membered rings into a (7 -i- 5)-membered bicyclic system in which C-17 exocyclic... 

Scheme 23 Spirolactones 82 via a tandem Wagner-Meerwein-type/lactonization process...

Cristol has continued his studies on the photo-Wagner-Meerwein processes in compounds of the type shown in (205). In this instance the influence of aryl substitution was examined. Other studies have reported the photochemical behaviour of the dibenzo-octadiene (206) and the octadienes (207). ... 

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