Methods for the cleavage of allylic and propargylic C-N bonds in amines and amides - Selected alternative applications of the 1,3-hydrogen shift

The aim of this article is to provide an updated review on the various methodologies that allow allylic C-N bonds (and by extension propargylic C-N bonds) to be cleaved. Since selectivity is crucial for synthetic planning, as far as possible, the relative reactivity of the various allylic groups is examined, and the discrimination between O-allyl and N-allyl derivatives is discussed. A special development is devoted to reactions leading to enamines through a 1,3-hydrogen shift, even though some of these reactions were not originally performed for the purpose of cleaving the N-allyl bond. Some selected applications are discussed. In addition to preparative deprotection methods, reactions such as the enzyme-mediated cleavage of allylic C-N bonds are also mentioned, although these reactions may not have any practical synthetic interest at the moment.