Hemiacetal Esters: Synthesis, Properties, and Applications of a Versatile Functional Group

The present perspective provides an overview of the hemiacetal ester (HAE) chemical functionality and its use in organic synthesis and polymer science. The objective is to expose the high potential of the HAE functionality in both molecular and macromolecular chemistry through highlighting its rich and peculiar reactivity and describing the achievements in polymer chemistry involving this group. We present a summary of the different synthetic routes described so far to produce HAEs, whether this led to linear or cyclic compounds. We also outline the very rich and complex reactivity of the HAE functional group through a thorough description of its dissociation under a thermal or ionic stimulus, its hydrolysis/alcoholysis susceptibility, and its ability to undergo exchange reactions. Finally, the successful use of HAEs for various applications in organic and polymer chemistry is also described, including, but not limited to, their use as protecting groups, initiators of polymerization, building blocks in polymer synthesis, or exchangeable linkages in covalent adaptable networks.