Acetohydrazone: A Transient Directing Group for Arylation of Unactivated C(sp(3))-H Bonds.

A straightforward and efficient method has been developed for the synthesis of 2-benzylbenzaldehyde derivatives from 2-methylbenzaldehyde and iodobenzene via a C(sp(3))-H activation process. In the course of the activation reaction, acetohydrazone is formed between 2-benzylbenzaldehyde and acetohydrazine as a transient directing group. As a new kind of transient directing group, acetohydrazone exhibits a remarkable directing effect to give corresponding products in good to excellent yields.