Transposition reactions 1.3- heteroatom-hydrogen

Heteroatom to hydrogen transpositions in allylic systems (equation 43) can be observed in different reactions, namely Ae protonation of allyl metal compounds, in reductions of allyl heterocompounds and in retro-ene reactions. Except for the last reaction, which proceeds by a cyclic transition state, the problem of regioselectivity restricts the synthetic value of such reactions and it is only in specific cases that this can be overcome. 

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