Efficient Multi‐component Synthesis of Highly Substituted Imidazoles Utilizing P2O5/SiO2 as a Reusable Catalyst

Phosphorus pentoxide supported on silica gel (P₂O₅/SiO₂) has been used as an efficient and reusable catalyst for the one‐pot pseudo four‐component synthesis of 2,4,5‐trisubstituted imidazoles from benzil or benzoin, aldehydes, and ammonium acetate. It was also used for four‐component preparation of 1,2,4,5‐tetrasubstituted imidazoles from benzil or benzoin, aldehydes, primary amine, and ammonium acetate under thermal solvent‐free conditions. The remarkable features of this new procedure are high conversions, cleaner reaction, simple experimental and work‐up procedures and also the catalyst can be easily separated from the reaction mixture and reused several times without any loss of its activity.     

Rapid and Facile Access to Indeno[1,2‐d]imidazoles via a Tandem Addition?Cyclization Reaction

A novel and tandem synthesis of highly functionalized tetrahydroindeno[1,2‐d]imidazole is described. A one‐pot reaction between a primary amine, an aryl isothiocyanate, and ninhydrin leads to highly substituted indeno[1,2‐d]imidazoles under solvent‐free conditions in excellent yields (Scheme). Their structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses.     

Synthesis of Azoles with Two Pyridine Substituents at Carbon Atoms and Their Use in Coordination Chemistry. (Review)

Published data on the synthesis of azoles containing two pyridine substituents are analyzed in relation to the type of central five-membered ring. The applications of such molecules as ligands in coordination chemistry are discussed. Dedicated to Academician Nikolai Serafimovich Zefirov in honor of his seventieth birthday. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1290–1301, September, 2005.     

Highly Efficient,Four Component,One-pot Synthesis of Tetrasubstituted Imidazoles Using a Catalytic Amount of FeCl<Subscript>3</Subscript> · 6H<Subscript>2</Subscript>O

Summary. An efficient and improved procedure for the synthesis of tetrasubstituted imidazoles by FeCl₃ · 6H₂O catalyzed four-component one-pot synthesis in refluxing ethanol is described.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

A Transition‐Metal‐Free Synthesis of Multisubstituted Imidazoles

A novel and simple t‐BuOLi/I₂‐mediated synthesis of 1,2,4‐trisubstituted imidazoles was developed without transition‐metal added. The transition‐metal‐free strategy tolerated a range of substrates and provided products in moderate to good yields with 100% regioselectivity.     

Switchable [3+2] and [4+2] Heteroannulation of Primary Propargylamines with Isonitriles to Imidazoles and 1,6‐Dihydropyrimidines: Catalyst Loading Enabled Reaction Divergence

Isonitrile 1 due to its carbene‐like reactivity serves generally as a one‐carbon synthon in a diverse set of organic transformations. We report in this article that the isocyano group can also act as a polarized triple bond to undergo, as a two‐atom synthon, heteroannulation with primary propargylamines 15 . In addition, we serendipitously discovered that the reaction pathways can be modulated by simply changing the catalyst loading. In the presence of 0.1 equiv of Yb(OTf)₃ or TfOH, the reaction between 1 and 15 afforded exclusively imidazoles 16 by a formal [3+2] cycloaddition. At a higher catalyst loading (Yb(OTf)₃ (0.4 equiv) or TfOH (0.5 equiv)) under otherwise identical conditions, the same reaction furnished 1,6‐dihydropyrimidines 17 in good to excellent yields by way of a formal [4+2] cycloaddition process. Mechanistic investigations indicated that both annulations went through an amidine intermediate resulting from the insertion of the isocyano group to the NH bond of the primary amine. Subsequent catalyst‐loading‐dependent 5‐exo‐dig or 6‐endo‐dig cyclization provided selectively the two heterocycles, respectively.     

Synthese und Koordination von 2-Acetylimino-1,3-dimethylimidazolin. Die Kristallstruktur von [Cu4I4(C7H11N3O)2] [1]

Synthesis and Coordination of 2-Acetylimino-1,3-dimethylimidazoline. The Crystal Structure of [Cu₄I₄(C₇H₁₁N₃O)₂] 2-Acetylimino–1,3-dimethylimidazoline ( 2 , ImNAc) obtained from 1,3-dimethyl-2-iminoimidazoline ( 1 ) and acetyl chloride forms with CuI the stepped cubane type complex [Cu₄I₄(ImNAc)₂] ( 3 ); the X-ray structure of 3 is reported.     

Synthesis and Characteristics of Organic Red‐Emissive Materials Based on Phenanthro[9,10‐d]imidazole

Red emission is one of the three primary colors that are essential for the realization of full‐color displays and solid‐state lightings. A high solid‐state efficiency is a crucial factor for the applications in organic light‐emitting diodes (OLEDs). In this work, two new donor‐acceptor‐donor type phenanthro[9,10‐d]imidazole (PIM)‐based derivatives, (2Z,2′Z)‐2,2′‐(1,4‐phenylene)bis(3‐(4‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)phenyl)acrylonitrile) ( PIDSB ) and 2,3‐bis(4′‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)‐[1,1′‐biphenyl]‐4‐yl)fumaronitrile ( PIDPh ), are designed and synthesized. Both of them possess high thermal stabilities. PIDPh shows typical characteristics of aggregation‐induced emission enhancement, while PIDSB displays an aggregation‐caused quenching effect. They both exhibit significant red‐shifted emissions compared with PIM owing to intramolecular charge transfer. In the film state, the emission peaks of PIDSB and PIDPh are located at 538 nm and 605 nm with high photoluminescent quantum yields of 63.82 % and 41.26 %, respectively. The non‐doped OLED using PIDPh as the active layer shows the maximum external quantum efficiency of 2.06 % with a very low efficiency roll‐off, and exhibits the electroluminescent peak at 640 nm with a Commission Internationale de l′Éclairage coordinate of (0.617,0.396), meeting well the criteria of red OLEDs.     

Synthesis of a new isomer of creatinine and its use in the preparation of the food mutagen 2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine (PHIP)

Base-induced cyclization of N′-cyanomethyl-N′-methylurea gives 1-methyl-4-amino-imidazol-2-one, this in turn is condensed with 3-hydroxy-2-phenylacrolein to yield an imidazo[4,5-b]pyridine which is converted into 2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine (PHIP).