Rh(III)- and Ir(III)-Catalyzed C–H Alkynylation of Arenes under Chelation Assistance

An
efficient Rh­(III)- and Ir­(III)-catalyzed, chelation-assisted
C–H alkynylation of a broad scope of (hetero)­arenes has been
developed using hypervalent iodine-alkyne reagents. Heterocycles, N-methoxy imines, azomethine imines, secondary carboxamides,
azo compounds, N-nitrosoamines, and nitrones are
viable directing groups to entail ortho C–H
alkynylation. The reaction proceeded under mild conditions and with
controllable mono- and dialkynylation selectivity when both mono-
and dialkynylation was observed. Rh­(III) and Ir­(III) catalysts exhibited
complementary substrate scope in this reaction. The synthetic applications
of the coupled products have been demonstrated in subsequent derivatization
reactions. Some mechanistic studies have been conducted, and two Rh­(III)
complexes have been established as key reaction intermediates. The
current C–H alkynylation system complements those previously
reported under gold or palladium catalysis using hypervalent iodine
reagents.