Benzoanellated [2.2]Paracylophanes: Synthesis and Electronic Properties

Abstract

Mono- and dibenzoannelated [2.2]paracyclophanes 12 and 1 were synthesized by palladium-catalyzed twoand
four-fold alkenylation of vicinal di- and tetrabromides 5 and 6, respectively, and subsequent electrocyclization/
dehydrogenation of the resulting (E,Z,E)-trienes. Further extensions of the annelated ring systems, leading to the
tetrahydronaphthalene derivative 15, the bis-terphenylene derivative 16, and the benzobis[2.2]paracyclophane 18, were
achieved through derivatization of suitable substituents introduced with the alkene coupling component. Mono- and
polyanions of some derivatives were generated and studied by ESR, ENDOR, and NMR spectroscopy, as well as by
cyclic voltammetry. The assembly of mutually orthogonal r-systems in arene annelated [2.2]paracyclophanes allows
the reversible incorporation of up to six additional electrons per molecule, which is the upper limit for hydrocarbons
reported to date.