Heterogeneous copper-catalyzed decarboxylative cyclization of 2-benzoylpyridines with α-amino acids leading to imidazo[1,5-a]pyridines

Abstract

The heterogeneous decarboxylative cyclization reaction between 2-benzoylpyridines and α-amino acids was achieved in toluene at 120 °C in the presence of 15 mol% of l-proline-functionalized MCM-41-supported copper(II) complex [l-Proline-MCM-41-Cu(OTf)2] and iodine with di-tert-butyl peroxide (DTBP) as oxidant, yielding a variety of 1,3-disubstituted imidazo[1,5-a]pyridines in good to excellent yields. The new supported copper catalyst can be prepared from commercially available and inexpensive reagents, and recovered from the reaction mixture by a simple filtration and recycled up to eight times with almost consistent activity.