Ten 1,2,4,5-tetra-substituted imidazole derivatives have been synthesized with a 2-hydroxyethy substituent at the 1-nitrogen atom and potentially electron releasing hydroxy-, methoxy-, dimethylamino- or nitro substituents in various positions on the benzene ring located on the 2-carbon atom. The prototypical derivative with an unsubstituted phenyl ring at the 2-position is also reported. The compounds are obtained in excellent yields (average 86%) via a four-component cyclocondensation reaction of benzil, ethanolamine, and the appropriate aromatic carbaldehyde together with ammonium acetate. The reaction uses a novel ionic liquid catalyst, DEAHS (diethyl ammonium hydrogen sulfate), under solvent-free conditions and a green synthetic protocol. The key advantages of this process are high yield, shorter reaction times and ease of work-up. Furthermore, the products can be purified by a non-chromatographic method and the catalyst is re-usable. All of these newly synthesized compounds have been characterized from spectral data; the X-ray structures of three representative molecules are also detailed.

Key indicators: single-crystal X-ray study; T = 93 K; mean (C-C) = 0.002 Å; R factor = 0.048; wR factor = 0.132; data-to-parameter ratio = 18.2.The title compound, C 27 H 28 N 2 O, is a lophine (2,4,5-triphenyl-1H-imidazole) derivative with an n-pentyl chain on the amine N atom and a 4-methoxy substituent on the benzene ring. The two phenyl and methoxybenzene rings are inclined to the imidazole ring at angles of 25.32 (7), 76.79 (5) and 35.42 (7) , respectively, while the methoxy substituent lies close to the plane of its benzene ring, with a maximum deviation of 0.126 (3) Å for the methoxy C atom. In the crystal, inversion dimers linked by pairs of C-HÁ Á ÁO hydrogen bonds generate R 2 2 (22) loops. These dimers are stacked along the a-axis direction. Related literature

The mechanisms of a tetrasubstituted imidazole [2‐(2,4,5‐triphenyl‐1 H‐imidazol‐1‐yl)ethan‐1‐ol] synthesis from benzil, benzaldehyde, ammonium acetate, and ethanolamine in [Et2NH2][HSO4] ionic liquid (IL) are studied computationally. The effects of the presence of the cationic and anionic components of the IL on transition states and intermediate structures, acting as a solvent versus as a catalyst, are determined. In IL‐free medium, carbonyl hydroxylation when using a nucleophile (ammonia) proceeds with a Gibbs free energy (ΔG ≠) barrier of 49.4 kcal mol−1. Cationic and anionic hydrogen‐bond solute–solvent interactions with the IL decrease the barrier to 35.8 kcal mol−1. [Et2NH2][HSO4] incorporation in the reaction changes the nature of the transition states and decreases the energy barriers dramatically, creating a catalytic effect. For example, carbonyl hydroxylation proceeds via two transition states, first proton donation to the carbonyl (ΔG ≠=9.2 kcal mol−1) from [Et2NH2]+, and then deprotonation of ammonia (ΔG ≠=14.3) via Et2NH. Likewise, incorporation of the anion component [HSO4]− of the IL gives comparable activation energies along the same reaction route and the lowest transition state for the product formation step. We propose a dual catalytic IL effect for the mechanism of imidazole formation. The computations demonstrate a clear distinction between IL solvent effects on the reaction and IL catalysis.

The title compound, C26H25N3, crystallizes with four independent mol­ecules, 1–4, in the asymmetric unit of the triclinic unit cell. The allyl substituents on the imidazole rings adopt similar conformations in all four mol­ecules. The imadazole and the 4-and 5-substituted phenyl rings of two pairs of molecules in the asymmetric unit stack parallel to (110). In contrast, the dimethyl­aniline systems in these pairs of mol­ecules are almost normal to one another, with dihedral angles of 85.84 (10) and 85.65 (10)° between the benzene rings of the two dimethyl­aniline fragments of mol­ecules 1 and 2, and 3 and 4, respectively. The crystal structure features an extensive series of C—H⋯π inter­actions that link the mol­ecules into undulating rows along the c axis. The crystal studied was a pseudo-merohedral twin with twin law [-100, 0-10, 111] and the BASF parameter refined to 0.513 (3).