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  palauchlor  , 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 -systems , sulfonamides , 
 and silyl enol ethers . 
 comparisons with other known chlorinating reagents 
 revealed cbmg to be the premier reagent .