Rearrangement of halogen compounds

Lucas and Jameson61 showed that at 248° 1-bromobutane is converted slowly but completely into 2-bromobutane but this reaction has no preparative importance. 

Very much milder conditions suffice for the conversion of a bromo / -oxo esters into y-bromo / -oxo esters 62 

According to Reid and Fortenbauch,63 bromination of ethyl 2,5-dimethyl-3-oxohexanoate in chloroform and storage overnight leads to production of the 4-bromo derivative from the 2-bromo derivative that is formed initially. 

Such rearrangements are particularly common among brominated steroidal ketones.64 Bromination of a steroidal ketone usually affords first the axial bromo ketone which can pass into the stable equatorial isomer in a reaction catalysed by hydrogen bromide 65 

For example, 2/ (flx)-bromo-5 -cholestan-3-one is so unstable that it cannot be obtained pure and passes into the equatorial isomer even on filtration of its benzene solution over aluminum oxide.66 

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