title: Intramolecular domino electrophilic and thermal cyclization of peri-ethynylene naphthalene oligomers.
abstract: The intramolecular electrophilic or thermal cyclization of arylene ethynylene precursors recently became a powerful method for the synthesis of new polycyclic aromatic hydrocarbons (PAHs). In this work, we investigated in detail the synthesis and intramolecular cyclization reaction of a series of peri-ethynylene naphthalene oligomers in which the ethynylene units are fixed in close proximity within the naphthalene framework. The high reactivity of these precursors led to simultaneous thermal cyclization reactions, even during their syntheses. Electrophilic cyclizations with iodine were also undertaken. Several new PAHs containing five-membered rings, for example, indeno[2,1-a]phenalene, acenaphtho[1,2-a]pyrene, and benzo- or naphtho-annulated fluoranthene derivatives, were synthesized and their structures were unambiguously determined by X-ray crystallographic analysis. Plausible mechanisms were proposed and it was demonstrated that oligomers most probably underwent intramolecular domino cyclization via either radical or cationic intermediates. The photophysical and electrochemical properties of these new PAHs were investigated and some of them displayed amphoteric redox behavior, due to the existence of five-membered rings.
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Huang
authors.forename: Lintao
authors.initials: L
authors.lastname: Zeng
authors.forename: Zebing
authors.initials: Z
authors.lastname: Zeng
authors.forename: Jishan
authors.initials: J
authors.lastname: Wu