Overcoming the Challenges toward Selective C(6)–H Functionalization of 2‑Pyridone with Maleimide through Mn(I)-Catalyst: Easy Access to All-Carbon Quaternary Center

An earth-abundant and inexpensive Mn­(I)-catalyzed alkylation of 2-pyridone with maleimide has been reported for the first time, in contrast to previously reported Diels–Alder products. Notably, an unexpected rearrangement has been discovered in the presence of acetic acid, which also provides a unique class of compounds bearing three different N-heterocycles with an all-carbon quaternary center. Furthermore, single crystal X-ray and HRMS revealed a five-membered manganacycle intermediate. This methodology tolerates a wide variety of functional groups delivering the alkylated products in moderate to excellent yields.