Thermal and Microwave-Assisted Rapid Syntheses of Substituted Imidazo[1,2-a]pyridines Under Solvent- and Catalyst-Free Conditions

Abstract

Thermal and microwave-assisted rapid syntheses of highly substituted imidazo[1,2-a]pyridine derivatives by reaction of aminopyridines and α-bromo-β-keto esters under solvent-free conditions are described. Reactions carried out under microwave irradiation give the highest yields of products in reaction times of less than two minutes.

aminopyridines - α-bromo-β-keto esters - imidazo[1,2-a]pyridines - microwave irradiation - solvent-free - thermal

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X-ray crystal data for 5g: empirical formula: C₁₇H₁₆N₂O₂, formula weight: 280.32, T = 293(2) K, λ = 0.71073, crystal system: monoclinic, space group: P21/c, unit cell dimensions: a = 11.419(3) Å, b = 14.292(4) Å, c = 9.001(2) Å, β = 99.912(4)˚, V = 1447.1(6) Å^³, Z = 4, density (calcd) = 1.287 mg/m^³, absorption coefficient: 0.086 mm^-¹, F(000) = 592, crystal size: 0.32 × 0.21 × 12 mm, reflections collected: 7540, independent reflections: 2813, R _{( int)} = 0.0225, data/restraints/parameters: 2813/0/193, goodness-of-fit on F ^² = 1.151, final R indices [I ≥ 2σ(I)], R1 = 0.0623, wR2 = 0.1392, R indices (all data): R1 = 0.0742, wR2 = 0.1456, largest diff. peak and hole: 0.204 and -0.219 eÅ^-³. CCDC 793451 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

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