A Review of Uncommon Transformations in Enaminone Chemistry

The applicability of enaminones is based on its reactivity allowing usage of the compound in other than nucleophilic addition and cyclization processes. Recent literature revealed several novel reactions that expand their synthetic usage. As perhaps one of the most unusual emerging reactivity patterns of enaminones are their engagements in intramolecular cyclization and their ability to form heterocycles at mild conditions. Functionalized enaminones also demonstrate nucleophilic activity in their reactions with different electrophiles, including alkylating agents as well as carbonyl compounds, making bond formation that cannot be easily predicted. Further, enaminones undergo redox-active type transformations including oxidative coupling and construction of C─N bonds, which direct the synthesis of polyfunctional amines and nitrogen-containing frameworks. They also participate in radical processes such as cross-coupling and polymerization reactions, expanding their activity spectrum. These unprecedented reactivity patterns of enaminones provide us with new strategies for building up sophisticated molecular architectures and functional materials. This review focuses on the new reactivity trends of enaminones for constructing new classes of compounds and suggests the perspectives of their usage in subsequent studies to advance synthetic chemistry.