Ni(ii)–salt catalyzed activation of primary amine-sp³C_α–H and cyclization with 1,2-diketone to tetrasubstituted imidazoles

Abstract

NiCl2·6H2O and Ni(OAc)2·4H2O were found as efficient catalysts for C-H activation of benzyl and aliphatic amines for an unprecedented multi C-N bond forming cyclization with 1,2-diketones under refluxing toluene to furnish highly substituted and polycyclic imidazoles.

Synthesis of Polysubstituted Imidazoles and Pyridines via Samarium(III) Triflate‐Catalyzed [2+2+1] and [4+2] Annulations of Unactivated Aromatic Alkenes with Azides

“…1‐(4‐Methylbenzyl)‐4,5‐diphenyl‐2‐ p ‐tolyl‐1 H ‐imidazole (3b): white solid; mp 135–137 °C (lit 15. 132–135 °C); 1 H NMR (500 MHz, CDCl 3 ): δ =7.58–7.54 (m, 4 H), 7.36–7.29 (m, 3 H), 7.24–7.18 (m, 6 H), 7.15–7.12 (m, 1 H), 7.01 (d, J =7.9 Hz, 2 H), 6.70 (d, J =8.0 Hz, 2 H), 5.06 (s, 2 H), 2.37 (s, 3 H), 2.29 (s, 3 H); 13 C NMR (125 MHz, CDCl 3 ): δ =148.2, 138.8, 137.9, 136.9, 134.7, 134.6, 131.2, 131.1, 130.9, 129.9, 129.3, 129.3, 128.9, 128.8, 128.6, 128.1, 126.9, 126.3, 125.9, 48.0, 21.4, 21.1; HR‐MS (ESI‐ion trap): m/z =415.2181, calcd.…”

“…1‐Benzyl‐4,5‐bis(4‐bromophenyl)‐2‐phenyl‐1 H ‐imidazole (3o): white solid; mp 132–133 °C (lit 15. 128–131 °C); 1 H NMR (500 MHz, CDCl 3 ): δ =7.65–7.61 (m, 2 H), 7.45 (d, J =8.4 Hz, 2 H), 7.42–7.40 (m, 5 H), 7.34 (d, J =8.6 Hz, 2 H), 7.24–7.21 (m, 3 H), 7.04 (d, J =8.4 Hz, 2 H), 6.82–6.76 (m, 2 H), 5.09 (s, 2 H); 13 C NMR (125 MHz, CDCl 3 ): δ =148.66, 137.5, 137.1, 133.1, 132.5, 132.2, 131.3, 130.5, 129.7, 129.2, 129.0, 128.9, 128.8, 128.7, 128.4, 127.6, 125.9, 123.3, 120.5, 48.5; HR‐MS (ESI‐ion trap): m/z =545.0056, 543.0078, calcd.…”

Iodine-Catalyzed Functionalization of Primary Aliphatic Amines to Oxazoles, 1,4-Oxazines, and Oxazinones

“…Thus, use of prefunctionalized amines, directing group (DGs), and/or transient DG, their removal after the desired transformation, and intramolecular annulation are frequently exercised in the metal catalysis processes. 15−18 A limited number of approaches were devoted for the site-selective C(sp 3 )-H functionalization of primary aliphatic amines, such as Zr IV /Ni II -catalyzed α-selective cyclization, 19,20 Pd II -tuned β-arylation, 21 Pd II -Ag I guided γ-substitution, 18,22−25 and Pd II -activated δ-arylation. 26,27 However, a metal-free C(sp 3 )-H functionalization is always a more appealing strategy to be developed for minimizing the harmful impact on nature.…”

A Greener and Facile Synthesis of Imidazole and Dihydropyrimidine Derivatives under Solvent‐Free Condition Using Nature‐Derived Catalyst

“…The classical synthesis of aforesaid derivatives was performed in a harsh condition, where the reaction was catalyzed in presence of formaldehyde in ammonia or lewis/bronsted acids ,. Subsequently, several approaches were reported for the synthesis of imidazoles as well as for dihydropyrimidines, which were developed either by the use of expensive catalysts or by some hazardous organic solvents . In spite of the availability of numerous synthetic methodologies, most of these techniques involved the use of expensive chemicals, air sensitive catalysts, special efforts for the preparation of the starting materials and use of toxic organic solvents etc.…”