A new synthetic route to substituted tetracenes and pentacenes via stereoselective [4+2] cycloadditions of 1,4-dihydro-1,4-epoxynaphthalene and isobenzofuran†
Stereoselective [4+2] cycloadditions of 1,4-dihydro-1,4-epoxynaphthalene and isobenzofuran were described. Among several possibilities, syn–exo and/or anti–endo isomers were selectively produced depending on the substitution pattern of the reactants. Importantly, the syn–exo isomer underwent acid promoted aromatization, affording the corresponding tetracene. These findings enabled us to prepare a substituted pentacene with electron withdrawing groups.