Systematic Synthesis Loads Up Aromatics

Benzene is the quintessential aromatic molecule and serves as an indispensable building block of pharmaceuticals, plastics, and more. Yet chemists have never gotten around to developing a general approach for substituting benzene with six different aryl groups, meaning that benzene’s structural diversity is far from being exhausted. Kenichiro Itami, Junichiro Yamaguchi, and coworkers of Nagoya University, in Japan, have decided to have a go at filling this void. By taking advantage of the richness of organic synthesis, the researchers created a programmed approach (shown) for preparing hexaarylbenzenes as well as multisubstituted naphthalenes and pyridines (Nat. Chem. 2015, DOI: 10.1038/nchem.2174). The team studied many synthetic methodologies and found that by starting with 3-methoxythiophene and using a combination of C–H activation, cross-coupling, and [4+2] cycloaddition reactions they can systematically prepare multisubstituted aromatics. Although the Nagoya chemists have made a variety of new compounds, they estimate that with the array of substituents at hand, more than 1 billion hexaarylbenzenes are still waiting to be made.