Recent Advances in Synthetic Methods for 2H‐Pyrroles

Abstract

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.

Stable 2-Azaallyl Salts as a Bridge between 2H-Azirines and Densely Functionalized 2H-Pyrroles

“…The nonaromatic 2 H -pyrrole ring is an important heterocyclic system encountered in natural products and is also used as a valuable intermediate in organic synthesis . There are several strategies for the preparation of 2 H -pyrroles including dearomatization of 1 H -pyrroles, transformations of other pyrrole and azole derivatives, cycloaddition reactions of alkynes with isocyanides, and cyclization of alkynylated enaminones . 2 H -Pyrroles has also been prepared by the two-step procedure “transannulation of 2 H -azirines with inamides into 3 H -pyrroles/acid-catalyzed thermal isomerization” .…”

Asymmetric magnesium catalysis for important chiral scaffold synthesis

“…Recently, our group has reported an enantioselective [3 + 2] reaction between α-isocyanoacetates and alkynyl ketones for efficient synthesis of optically active 2 H -pyrrole structures. 50,51 The reaction utilized a prolinol-derived chiral ligand L34 for in situ generation of a magnesium catalyst. Notably, an interesting aluminium-mediated chirality maintaining 1,5-ester shift reaction was discovered for the construction of enantioenriched 3 H -pyrroles as well (Scheme 17d).…”