Huisgen-White rearrangement

During the synthesis of 436, Muraoka and colleagues produced the diazobi-cyclo[4.3.1]decane 435 via the classical ring expansion (equation 184). Huisgen-White rearrangement of the cyclic lactam leads to 436, a key synthetic intermediate for piperidine alkaloids. 

The rearrangement of N-alkyl-N-nitrosoamides has contributed much to the delineation of scheme 5. The reaction has been shown to proceed with the formation of a diazoester intermediate which fragments to a diazonium ion pair as shown below (White, 1955 White and Aufder-marsh, 1961b Huisgen and Reimlinger, 1956a and b). 

It is possible that similar behaviour is responsible for the rather surprising finding that the product obtained from reaction of the carbonium ion with solvent in the rearrangement of nitrosoamides in aqueous or ethanolic solution is also of retained configuration (Huisgen and Riichardt, 1956b White and Elliger, 1967). 

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