Photoinduced Palladium-Catalyzed Site-Selective Meta-Alkylation of Pyridines
byAnurag Singh, Rajesh Kancherla, Sayan Dutta, Arnab Dey, Kuntal Pal, Bholanath Maity, Lennard Kloene, Luigi Cavallo, Rene M. Koenigs, Magnus Rueping
Year:2026DOI:10.1002/ange.5426146
Extra Information
Angewandte Chemie International Edition
Abstract
Achieving regioselective meta-C–H alkylation of pyridines remains
a long-standing challenge due to their intrinsic electronic bias and
the lack of general strategies compatible with simple alkyl
electrophiles. In contrast to Minisci-type alkylations, which
preferentially functionalize electron-deficient positions, meta-alkylation
of unbiased pyridines using alkyl bromides has remained elusive.
Herein, we report a photoinduced palladium-catalyzed strategy that
enables regioselective meta-alkylation of pyridines with
commercially available alkyl bromides via a redox-neutral
dearomatization pathway. Visible-light excitation of palladium generates
a hybrid alkyl–Pd(I) radical species that undergoes regioselective
addition to oxazino-pyridine intermediates despite inherent polarity
mismatch, forming a stabilized π-allyl Pd(I) radical prior to
rearomatization. The method exhibits a broad substrate scope
encompassing diverse pyridines, quinolines, and alkyl bromides, and
enables one-pot and sequential meta-functionalization strategies.
DFT calculations support an outer-sphere radical addition mechanism and
rationalize the observed regioselectivity. This work establishes a new
paradigm for Pd-catalyzed meta-C–H alkylation of azines, a complementary conceptual approach to conventional and important Minisci chemistry.