Palau’chlor: A Practical and Reactive Chlorinating Reagent

Unlike its other
halogen atom siblings, the utility of chlorinated
arenes and (hetero)­arenes are twofold: they are useful in tuning electronic
structure as well as acting as points for diversification via cross-coupling.
Herein we report the invention of a new guanidine-based chlorinating
reagent, CBMG or “Palau’chlor”, inspired by a
key chlorospirocyclization en route to pyrrole imidazole alkaloids.
This direct, mild, operationally simple, and safe chlorinating method
is compatible with a range of nitrogen-containing heterocycles as
well as select classes of arenes, conjugated π-systems, sulfonamides,
and silyl enol ethers. Comparisons with other known chlorinating reagents
revealed CBMG to be the premier reagent.