Dihydroazulene/Vinylheptafulvene Photoswitch: Ultrafast Back Reaction Induced by Dihydronaphthalene Annulation

Abstract

AbstractThe vinylheptafulvene (VHF) to dihydroazulene (DHA) electrocyclization is known to proceed from an s‐cis conformation of VHF and cannot occur from the more stable s‐trans conformation. Locking the VHF in the s‐cis conformation by the introduction of a dihydronaphthalene (DHN) unit has been found to greatly enhance the speed of this reaction. Thus, the half‐life was reduced by more than a factor of 150000 in cyclohexane and by a factor of approximately 950000 in ethanol. In addition, the characteristic absorption of the photoactive DHA isomer, now annulated to DHN, exhibited a desired redshift relative to the parent compound. Here, we present the synthesis and study of these DHN‐DHA/VHFs, including a protocol for the incorporation of a pseudo‐halide to enable the further functionalization of the molecule by metal‐catalyzed cross‐coupling reactions. For proof‐of‐concept, two different sulfur end‐groups were incorporated as anchoring groups for potential molecular electronics applications.