Synthesis of Acenes by Mechanochemical Reductive Aromatization.

A Sn-mediated mechanochemical reductive aromatization of 1,4-dihydroxy- and 1,4-dimethoxy-cyclohexadienes has been used to form 12 acenes, including derivatives of benzene, anthracene, tetracene, pentacene, and anthradithiophene. This method has been developed to overcome issues faced during the formation of electron-deficient 1,4-dihydroxy- or 1,4-dimethoxy-cyclohexadienes under homogeneous conditions. While this method does not tolerate trimethylsilyl protecting groups for alkynes, it can provide a fast and easily set up alternative to homogeneous reductive aromatization.