122409-37-4Relevant academic research and scientific papers
Substituent Dependency of the Dihydroazulene Vinylheptafulvene Photochromism: Steric and Electronic Effects of 9-Anthryl Compounds - New Access to Condensed Hydropentalenes
Gierisch, Sebastian,Bauer, Walter,Burgemeister, Thomas,Daub, Joerg
, p. 2341 - 2350 (2007/10/02)
The synthesis of 2-(9-anthryl)-1,8a-dihydro-1,1-azulenedicarbonitrile (1a) from 8-methoxyheptafulvene (3) by cycloaddition (via tetrahydroazulene 5a) and elimination of methanol is described.On irradiation with visible light 1a is transformed into the vinylheptafulvene 2a, which is reconverted into 1a under thermal conditions.The steric congestion caused by the 9-anthryl substituent determines the rate of the cycloaddition as well as the kinetics of the thermal back reaction 2a -> 1a and causes thermochromic behavior of dihydroazulene 1a.By intramolecular electrophilic substitution tetrahydroazulene 5a yields the condensed hydropentalene 9 which on oxidation leads to the condensed polycycle 11.The stereochemical assignments of the 9-anthryl compounds were achieved mainly by one- and twodimensional 1H-NMR spectroscopy. - Key Words: Aromatics, condensed / Cycloaddition / Azulenes, tetrahydro- / Photochromism / Thermochromism
