Demjanov rearrangement selectivity

Selectivity in rearrangement reactions is affected by the electronic nature of both the group that migrates and the group that is left behind. But there is more Stereochemistry is important too. The outcome of diazotization and semipinacol rearrangement (Tiffeneau-Demjanov rearrangement) of this amino-alcohol depends entirely on the diaster eoisomer you start with. There are four diastereoisomers, and we have drawn each one in the only conformation it can reasonably adopt, with the f-butyl group equatorial. 

Alkoxymethylamines 68 rather than hydroxymethylamines 32 and 38 have been shown to undergo the Tiffeneau-Demjanov rearrangement. This served to modestly alter the selectivity. ... 

Another example of the utility of this reaction is the formation of enantiopure cycloheptenones from optically pure natural products like R-carvone. Hydroxylaminomethylcyclohexene 72 derived from -carvone rearranged to provide two compounds resulting from selective rearrangement of the vinyl carbon. While the alkene migrated into conjugation under the reaction conditions providing 10% of 74, the Tiffeneau-Demjanov reaction provided entry into optically-enriched cycloheptenones. ... 

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