A novel method for the synthesis of imidazo[1,5-b]pyridazines

Abstract

Condensation of 4-phenylimidazole-1,2-diamine with 1-aryl-3-(dimethylamino)-2-propen-1-ones leads to the formation of 4-aryl-5-phenylimidazo[1,5-b]pyridazin-7-amines, which smoothly react at the exocyclic amino group with acetic anhydride, phenyl isocyanate, and para-tolualdehyde.

Interaction of 1,2-Diaminoimidazoles with Ethoxymythelene-Containing Compounds

“…As a polynucleophilic agent (1,3-C,N and 1,4-N,N) diaminoimidazole can form six-and seven-membered systems in the reaction with dielectrophilic agents. The determinative factor in the reaction direction are electrophile nature and conditions in which synthesis was performed [12][13][14][15][16].…”

A novel synthetic approach to hydroimidazo[1,5-b]pyridazines by the recyclization of itaconimides and HPLC–HRMS monitoring of the reaction pathway

“… Heterocyclization of 1-aminoimidazoles with 1,3-dicarbonyl or α,β-unsaturated carbonyl compounds (route B). Conditions: i) R 1 = NH 2 , NHAlk, R 2 = Ph, R 3,4 = Alk, Ar, solvent-free [ 24 ], AcOH [ 25 – 26 ], R 3 = Ph, R 4 = OEt, solvent-free [ 24 ]; ii) R 1 = NH 2 , R 2 = Ph, R 3 = H, Me, R 4 = Ar, ArCHO/MeOH/DMF [ 29 ] or R 4 = H, HC(OEt) 3 /iPrOH [ 30 ]; iii) R 1 = NH 2 , R 2 = Ar, R 3,4 = Alk, Ar, MeOH/ N -methylmorpholine or DMF or AcOH [ 27 – 28 ], R 3 = Ar, R 4 = COOH, DMF [ 31 ], R 3 = Ar, R 4 = NMe 2 , AcOH/DMF [ 32 ]. …”

“…In the synthesis of imidazo[1,5- b ]pyridazines along route B, 1-aminoimidazoles with no substituents at the C-5 atom of the original heterocycle and 1,3-dielectrophilic reagents are used, e.g., 1,3-diketones [ 24 – 26 ], β-ketoesters [ 24 ], α,β-unsaturated ketones [ 27 – 28 ], including those obtained in situ [ 29 – 30 ] or containing good leaving groups [ 31 – 32 ] ( Scheme 2 ).…”