Recent Advances in Synthetic Methods for 2H-Pyrroles

The compound, 2H-pyrrole, is a key scaffold contained in natural products, bioactive compounds, pharmaceuticals, and organic functional materials. However, the development of efficient synthetic strategies for 2H-pyrroles is challenging. This is because 2H-pyrroles, owing to their nonaromatic nature, are easily converted into the thermodynamically more stable 1H-pyrroles. Recently, efficient and straightforward synthetic strategies for 2H-pyrroles have been developed, including the dearomatization of 1H-pyrrole, oxidation of pyrrolines or pyrrolidines, ring construction via catalytic cycloaddition, and rearrangement of 3H-pyrroles. In this review, we summarize the progress in the research on 2H-pyrrole synthesis since 2000 and briefly discuss the synthesis reaction mechanisms.