Benzene comes of age. From Faraday's discovery to modern strategies for ring-opening of benzene.

The discovery of benzene by Michael Faraday in 1825 marked a pivotal moment in chemistry, arguably opening the vast field of organic chemistry and its enormous impact on mankind in terms of new pharmaceuticals, and materials. Over the past two centuries, the study of benzene has revealed its extraordinary stability due to its aromaticity resulting from its unique electronic distribution that makes its C-C bonds remarkably inert and resistant to chemical disruption. This feature has its advantages and the substitution/functional group chemistry is based on the knowledge that the benzene ring remains intact during the myriad changes that occur round its skeleton. But there has always been interest in exploring the possibility of ring-opening of the benzene ring. While early industrial and biochemical processes achieved ring-opening under extreme conditions, the quest for selective and mild methods to break the aromatic C-C bonds of benzene has remained elusive. Recent breakthroughs have ushered in new strategies for the activation of benzene, driven by advances in transition metal chemistry, particularly through multielectron-reduction/functionalization approaches. These innovations have led to the generation of acyclic products such as linear hexadiene, which can serve as valuable building blocks for optoelectronic materials. This review focuses on the progress in benzene ring-opening chemistry, highlighting the recent development of metal-mediated methods that cleave the aromatic ring under mild conditions, and discusses the potential applications and future directions of this area of research.