Synthesis of 2-Formylpyrroles from Pyridinium Iodide Salts

Abstract

The first I2-mediated synthesis of 2-formylpyrroles from pyridinium salts is reported. This protocol enables the synthesis of diversely substituted 2-formylpyrroles in good yields under operationally simple conditions. The detailed mechanistic studies reveal that the reaction proceeds via a novel H2O-triggered ring opening of the pyridinium salt and a subsequent intramolecularly nucleophilic addition sequence.

Solvent‐Free Strategy for Direct Access to Versatile Quaternary Ammonium Salts with Complete Atom Economy

“…Decomposition of the cyclic amino alcohol creates the aldehyde‐iodonium complex (d) . Intramolecular nucleophilic cyclization by attack of the iodonium to yield 2,3‐dihydro‐1 H ‐pyrrole (e) followed by dehydroiodination results in 4 a [19] …”

“…Intramolecular nucleophilic cyclization by attack of the iodonium to yield 2,3dihydro-1H-pyrrole (e) followed by dehydroiodination results in 4 a. [19] The five-membered 2-formylpyrroles can further transform to valuable molecules under mild conditions. As documented, the substituted pyrrole[2,3-d]pyridazin-4-ones as phosphodiesterase inhibitors IV can reduce inflammation and induce the relaxation of the bronchial smooth muscle (Scheme 6a).…”

Iodination/Amidation of the N-Alkyl (Iso)quinolinium Salts

“…We previously developed a novel approach for the preparation of 2-formylpyrroles by treating the pyridinium salts with I 2 (0.64 equiv) in the presence of K 2 CO 3 (4.0 equiv) in the mixed DCE/H 2 O solvent system . Meanwhile, when the quinolinium iodide salt A1 was subjected to that condition, unexpectedly, it led to the formation of a 7% yield of the iodination/amidation product 3-iodo-1-methylquinolin-2­(1 H )-one, the structure of which was unambiguously characterized by single-crystal X-ray diffraction analysis.…”

SuFEx‐Enabled Elastic Polysulfates for Efficient Removal of Radioactive Iodomethane and Polar Aprotic Organics through Weak Intermolecular Forces

“…According to previous reports, the salt formation is usually conducted at elevated temperature and in the presence of a large number of organic solvents, which is energy-consuming, time-consuming, and environmentally harmful. [30][31][32] Compared with the conventional method, a simple, fast, efficient and reusable gel-based iodomethane converter is proposed. Moreover, the gel can be easily recovered by a waterwashing and readsorption of pyridine method and reused at least 5 times (Figure 2b and S7).…”