Recent advances in the synthesis of N-heterocycles from α-amino acids mediated by iodine

The synthesis of N-heterocycles has received extensive attention from scientists considering their important role in organic synthesis, pharmaceuticals, and materials chemistry. alpha-Amino acids (alpha-AAs), both natural and non-natural, are structurally diverse, containing basic amino groups, acidic carboxyl groups, and various side-chain R groups in a single molecule. Given their structural properties and wide range of sources, they have undoubtedly become suitable synthetic building blocks for organic synthesis. However, conventional transformations of amino acids (AAs) focus on the amino and carboxyl groups independently. Conversions for these two prominent functional groups generally do not affect both their alpha positions and their branched chains. Over the past decade, with the application of iodine (I2) in the field of heterocyclic synthesis, the use of alpha-AAs for diverse construction of complex N-heterocyclic structures has gained increasing attention. This synthetic strategy relies on the I2-mediated Strecker degradation, which introduces alpha-AAs as electrophilic carbon species into the domino reaction sequence via decarboxylation and deamination processes. In this review, we have summarized recent advances in this emerging area.