Ammonium Salt-Catalyzed Highly Practical <i>Ortho</i>-Selective Monohalogenation and Phenylselenation of Phenols: Scope and Applications

An ortho-selective ammonium chloride salt-catalyzed
direct C–H monohalogenation of phenols and 1,1′-bi-2-naphthol
(BINOL) with 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) as the chlorinating
agent has been developed. The catalyst loading was low (down to 0.01
mol %) and the reaction conditions were very mild. A wide range of
substrates including BINOLs were compatible with this catalytic protocol.
Chlorinated BINOLs are useful synthons for the synthesis of a wide
range of unsymmetrical 3-aryl BINOLs that are not easily accessible.
In addition, the same catalytic system can facilitate the ortho-selective selenylation of phenols.