Chan−Evans−Lam coupling for the synthesis of N–aryl derivatives catalyzed by copper(I) chloride and sterically varied imidazolium salts at mild reaction conditions

First-row transition–metal–catalyzed organic transformations have received colossal interest in the modern synthetic organic chemistry due to their step– and atom–economic approaches. As a consequence, direct arylation of azoles through C–H or N–H activations acquired a broad spectrum of applications for accessing valuable small organic molecules that are of pharmaceutical interest. In this connection, sterically varied coumarin–functionalized imidazolium salts bearing bromide (5–7) and hexafluorophosphate anions (8–10) have been prepared and used as NHC precursors. The salts have been characterized by both, spectroscopic and analytical techniques. A hexafluorophosphate salt 9 was also studied for its structure using the single-crystal XRD technique. The salts that indeed, generate carbene that trap Cu(I) to form Cu(I)–NHC complexes in situ for the Chan−Evans−Lam C–N coupling of 1H–azoles/anilines and phenyl/thiopheneboronic acids, resulting in the formation of N–aryl derivatives in moderate to excellent yields. The structure-activity relationship studies revealed that the steric bulk around the metal center would help increase the catalytic Chan−Evans−Lam C–N coupling potential of the catalysts.