A terpyridine derivative and an iridium complex catalyze the C−H borylation of a stoichiometric amount of a fluoroarene with high ortho-selectivity and tolerance of functional groups such as bromide, chloride, ester, ketone, amine, and in situborylated hydroxyl. Complex drug molecules such as haloperidol can be selectively borylated ortho to the F atom. The terpyridine ligand undergoes rollover cyclometalation to produce an N,N,C-coordinated iridium complex, which may either selectively borylate the fluoroarene by itself or undergo reductive elimination to produce a borylated ligand.
We report here an efficient and easily
reproducible two-step approach
to heterocycle-substituted amino-pyrazoles from heterocyclic acetonitriles
and their unprecedented subsequent transformations to fully substituted
pyrazoles. Such transformations include regioselective derivatization
from polyamino derivatives, formation of tetracyclic compounds in
up to 45% overall yield, and deaminative transformations through diazotization,
followed by arylation through Suzuki–Miyaura cross-coupling
and C–H activation, providing arylated pyrazoles in up to 71%
yield over four steps. This strategy allows the swift introduction
of significant molecular complexity to a range of scaffolds.
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