Recent advances of deprotection of oximes, phenylhydrazones and semicarbazones

Abstract

Oximes, phenylhydrazones and semicarbazones are highly stable and useful carbonyl protective groups against the addition of nucleophiles. Oximes exist in syn and anti isomeric forms and can be employed in a variety of reactions, including acetylation, α-alkylation, rearrangement reactions, 1, 3-dipolar addition, addition reactions and ortho functionalization in addition to serving as the main building blocks for making derivatives of azirines, pyridines, oxazoles, oxazines and other heterocycles. Phenylhydrazones, when treated with Lewis acids, produce carbazoles with antibacterial properties. Moreover, protection-deprotection reactions are particularly useful in the total synthesis of organic compounds. Therefore, the cleavage of these imine derivatives into parent carbonyl compounds plays an important role in organic transformations. This review focuses on the deprotection of imine derivatives under various mechanistic aspects, which include single electron transfer (SET) and two electron transfer oxidative deprotection along with coordinative and protonative deprotection. Metal, non-metal and photo catalyzed reactions with atmospheric oxygen, as well as solvent-free, microwave and nano catalytic techniques are also described. The deprotection reactions from 2010 to March 2024 are covered in this review. For the readers benefit, a detailed discussion of the mechanisms underlying several significant reactions is included.