Synthesis of Luminescent Fused Imidazole Bicyclic Acetic Esters by a Multicomponent Palladium Iodide‐Catalyzed Oxidative Alkoxycarbonylation Approach

Abstract

A new multicomponent catalytic approach to important fused imidazole bicyclic acetic esters, whose core is present in many biologically active principles, is presented. It is based on the sequential cyclization‐alkoxycarbonylation‐isomerization of readily available N‐heterocyclic propargylamine derivatives, carried out under oxidative conditions using a simple catalytic system consisting of PdI2 (1 mol%) in conjunction with KI (1 equiv.), in the presence of AcONa as additive (1 equiv.) at 100 °C under 20 bar of a 4 : 1 mixture CO‐air. Under the optimized conditions, several N‐(prop‐2‐yn‐1‐yl)pyridin‐2‐amines were smoothly converted into alkyl 2‐(imidazo[1,2‐a]pyridin‐3‐yl)acetates in fair yields (51–77 %). The method was also applied to the conversion of N‐(prop‐2‐yn‐1‐yl)pyrimidin‐2‐amine into 2‐(imidazo[1,2‐a]pyrimidin‐3‐yl)acetate and of N‐(prop‐2‐yn‐1‐yl)pyrazin‐2‐amine into 2‐(imidazo[1,2‐a]pyrazin‐3‐yl)acetate. Some of the newly synthesized bicyclic derivatives have shown promising luminescence properties.

Cu‐Catalyzed Synthesis of Coumarin‐1,2,3‐Triazole Hybrids connected with Quinoline or Pyridine Framework**

“…5-Nitro-N-(prop-2-yn-1-yl) pyridine-2-amine (6) [46] and 1 in a similar reaction under Method A or B, but for a longer time, afforded triazole 7 in 68 % or 69 % yield, respectively (Table 2, entries 11,12). 4-Azidocoumarin (1) reacted, also, with 1-(prop-2-yn-1-yl) pyridine-2(1H)-one (8) [47] to furnish triazole derivative 9 in 93 % or 85 % yield under Method A or B, respectively (Table 2,entries 13,14).…”

A Stereoselective, Multicomponent Catalytic Carbonylative Approach to a New Class of α,β-Unsaturated γ-Lactam Derivatives

“…Based on the existing knowledge on carbonylations [1][2][3][4][5] and on our expertise in PdI 2 /KI-catalyzed carbonylation reactions [7,8], we can propose the mechanistic pathway shown in Scheme 2 for the formation of (Z)-2-(2-oxopyrrolidin-3-ylidene)acetates 2. Palladation of the nitrogen of 1 initially leads to alkynylaminopalladium intermediate I, stabilized by the intramolecular triple bond coordination (anionic iodide ligands are omitted for clarity).…”

“…In this work, a stereoselective, multicomponent catalytic carbonylative approach to a new class of α,β-unsaturated γ-lactam derivatives, that are, alkyl (Z)-2-(2-oxopyrrolidin-3ylidene)acetates 2, is presented. The synthetic approach is based on the use of a particularly simple catalytic system, consisting of PdI 2 in conjunction with KI [7,8], for the catalytic activation of very simple starting materials (homopropargylic amines 1, carbon monoxide, an alcohol, and oxygen; Scheme 1).…”

Recent Advances in the Synthesis of Five‐membered Nitrogen Heterocycles Induced by Palladium Ions and Complexes

“…Rapid reactions afforded medium to excellent yields in short treatment (Scheme 117). In a related study this method was also shown to be feasible to form imidazole bicyclic acetic esters under similar conditions but using alcohols instead of amines [140b] . The synthesis is based on carbonylation of N ‐heterocyclic propargylamine derivatives under oxidative conditions in the presence of sodium acetate.…”