Comparison of Linear and Cross‐Conjugation from Rates of Vinylheptafulvene Ring‐Closure. Issue 35 (29th October 2014)

• Record Type: Journal Article
• Authors: Fjelbye, Kasper; Christensen, Trine Nørgaard; Jevric, Martyn; Broman, Søren Lindbæk; Petersen, Anne Ugleholdt; Kadziola, Anders; Nielsen, Mogens Brøndsted
• Is Part Of: European journal of organic chemistry. Issue 35(2014)
• Page Start: 7859
• Page End: 7864
• Publication Date: 2014-10-29
• Subjects: Alkynes -- Conjugation -- Cross‐coupling -- Electrocyclic reactions -- Kinetics; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201403117
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract: The concept of cross‐conjugation has in recent years attracted increasing interest in materials science as well as in the field of molecular electronics as a means to tune the optical properties and molecular conductance of nanoscale devices. In this paper we show how the rate of an electrocyclic reaction, the conversion of vinylheptafulvene (VHF) into dihydroazulene (DHA), is influenced by an electron‐withdrawing p ‐nitrophenyl group separated from the VHF by either cross‐conjugated or linearly π‐conjugated bridging units. A selection of DHA/VHF molecules with ethyne, 1, 1‐ and 1, 2‐diethynylethene, and 1, 3‐butadiyne bridges was prepared by metal‐catalyzed coupling reactions. The effect of the different conjugated spacers on the kinetics of the conversion of VHF into DHA was examined by UV/Vis absorption spectroscopy by monitoring the decay of the VHF absorption. The cross‐conjugated diethynylethene spacer was found to increase the half‐life of the VHF relative to the linearly conjugated spacers. Abstract : The rate of electrocyclic ring‐closure of vinylheptafulvene (VHF) to dihydroazulene (DHA) has been studied for a series of compounds bearing a rate‐enhancing nitrophenyl group connected to the VHF through either a linear or cross‐conjugated bridge. The photoactive DHA compounds were prepared by metal‐catalyzed coupling reactions and converted into the VHFs by irradiation.