Recent advances in direct dehydrogenative biphenyl couplings

Biphenyl moiety represents a unique structural motif of many natural and unnatural products with biological interests, and dehydrogenative couplings of two aryl C-H bonds under oxidative conditions is unambiguously the most efficient and direct preparation of these compounds. However, higher oxidation potential of benzene derivatives makes such oxidative couplings much more difficult than other arenes. Only very limited advances have been achieved on direct formation of the crucial C-C bond between two phenyl derivatives by dehydrogenative phenyl coupling in the last two decades. This article briefly summarized and commented a number of representative recent achievements in this attractive field, including homo-, cross- and intramolecular rearrangement and couplings, as well as their applications in organic synthesis.