Ni(0)–Cu(i): a powerful combo catalyst for simultaneous coupling and cleavage of the C–N bond with cyclization to valuable amide-based pyrroles and 4-pyridones

Abstract

We demonstrate unprecedented Ni(0)–Cu(i) combo catalysis for sequential bond activated domino N–C/C–C coupled annulation with N–C bond cleavage to afford valuable amide-based polysubstituted pyrroles and 4-pyridones selectively from β-ketoanilides.

CuBr–ZnI2 Combo-Catalysis for Mild CuI–CuIII Switching and sp2 C–H Activated Rapid Cyclization to Quinolines and Their Sugar-Based Chiral Analogues: A UV–Vis and XPS Study

“…After several unsuccessful attempts using potential combo-catalysts − (entries 1–8, Table ), we used ZnI 2 –CuBr (10 mol % each) for the three-component reaction among 2-bromoaniline ( 1a , 1 mmol), 4-ethynyltoluene ( 2a , 1 mmol), and paraformaldehyde ( 3a , 1.2 mmol) in different solvents (entries 9–11, Table ) to achieve the 4-substituted quinoline 4a at room temperature in 60–65% yield. Gratifyingly, the yield (81%) and the reaction rate (30 min) significantly improved under the solvent-free conditions (entry 12).…”

“…Combo-catalysis is an emerging area, and we − and others − have established it as a powerful tool in modern organic synthesis. For instance, the diverse cyclization reactions catalyzed by VO­(acac) 2 –CeCl 3 , Ni(0)–Cu­(I), and Mo VI –CeCl 3 developed by our group provide easy access to a wide range of heterocycles. − CuBr–ZnI 2 -mediated N–N/C–N coupling for oxidative cyclization, Pd I –Ru I -mediated Suzuki cross-coupling reactions, AuClL n –AgSbF 6 -tuned C–C coupled aromatization, Ti–Cr-catalyzed polymerization reactions, and [IrCuCl 2 ] 2 –AgNTf 2 -guided amination through sp 2 C–H activation are very useful in the synthesis of combo-catalysis functionalized and sugar-based optically pure quinolines ( 4 ) under mild reaction conditions, with a significantly improved reaction rate, yield, and selectivity (without 5 ). Interestingly, Cu­(I/II) compounds − and organozinc­(II) were reported as active catalysts for the coupling of secondary aliphatic amines with aldehydes and alkynes with the respective propargyl amines.…”