A simple base-mediated halogenation of acidic sp2 C-H bonds under noncryogenic conditions.

A new method has been developed for in situ halogenation of acidic sp(2) carbon-hydrogen bonds in heterocycles and electron-deficient arenes. Either selective monohalogenation or one-step exhaustive polyhalogenation is possible for substrates possessing several C-H bonds that are flanked by electron-withdrawing groups. For the most acidic arenes, such as pentafluorobenzene, K(3)PO(4) base can be employed instead of BuLi for metalation/halogenation sequences.