Synthesis and Photochemical Characterization of Indolizine Fluorophores Obtained by a Multicomponent Palladium Iodide−Catalyzed Oxidative Aminocarbonylation Approach

A catalytic carbonylative method for the direct, multicomponent synthesis of indolizine fluorophores has been developed. The process is based on the PdI2/KI‐catalyzed oxidative aminocarbonylation of 2‐(pyridin‐2‐yl)pent‐4‐yn‐1‐carbonyl compounds leading to the corresponding 2‐ynamide intermediates,...

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Bibliographic Details
Published in:European journal of organic chemistry 2024-03, Vol.27 (12), p.n/a
Main Authors: Ziccarelli, Ida, Amuso, Roberta, Mancuso, Raffaella, Maggiore, Antonio, Lamberti, Giuseppe, Vitale, Paola, Maiorano, Vincenzo, Veltri, Lucia, Gabriele, Bartolo
Format: Article
Language:English
Subjects:
Carbonyl compounds
carbonylation
Carbonyls
Chemical compounds
cyclization
Fluorescence
fluorophores
indolizines
Nitrogen
Optical properties
Palladium
palladium catalysis
Synthesis
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Summary:A catalytic carbonylative method for the direct, multicomponent synthesis of indolizine fluorophores has been developed. The process is based on the PdI2/KI‐catalyzed oxidative aminocarbonylation of 2‐(pyridin‐2‐yl)pent‐4‐yn‐1‐carbonyl compounds leading to the corresponding 2‐ynamide intermediates, followed in situ by 5‐exo‐dig cyclization (by amine‐promoted conjugate addition of the pyridine ring nitrogen) and aromatization, to give the finally isolated N,N‐disubstituted 2‐(indolizin‐3‐yl)acetamides. Reactions are carried out under relatively mild conditions (100 °C under 20 atm of a 4 : 1 mixture CO−air for 6–15 h) in MeCN as the solvent and with a low catalyst loading (0.33 mol% PdI2), in the presence of 0.5 equiv. of KI and 3 equiv. of a secondary amine. The optical properties of representative 2‐(indolizin‐3‐yl)acetamide products have also been investigated. N,N‐disubstituted 2‐(indolizin‐3‐yl)acetamides with fluorescent properties are obtained in a multicomponent fashion starting from simple building blocks (2‐(pyridin‐2‐yl)pent‐4‐yn‐1‐carbonyl compounds, CO, amines, and oxygen) through a sequential PdI2/KI‐catalyzed oxidative aminocarbonylation – cyclization – aromatization process. Initially formed 2‐ynamide intermediates, ensuing from Pd‐catalyzed triple bond oxidative aminocarbonylation, are converted in situ into the final products by amine‐promoted intramolecular dearomative conjugate addition followed by rearomatization.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.202400013