Beilstein J. Org. Chem.2012,8, 958–966, doi:10.3762/bjoc.8.108
dihydroazulene (DHA)/vinylheptafulvene (VHF) system (with two cyano groups at C1) functions as a photo-/thermoswitch. Direct ionic bromination of DHA has previously furnished a regioselective route to a 7,8-dibromide, which by elimination was converted to a 7-bromo-substituted DHA. This compound has served as a
; photoswitch; vinylheptafulvene; Introduction
1,8a-Dihydroazulene-1,1-dicarbonitrile (DHA, 1) is a yellow photochromic compound, which undergoes a light-induced 10-electron retro-electrocyclization to a red-colored vinylheptafulvene (VHF) (Scheme 1) [1][2][3]. The VHF compound is formed as the s-cis conformer
selectively brominated to furnish the product 10.
Absorption spectra of DHA 8 and VHF 7 in cyclohexane. The broken curve shows the absorption spectrum after one light–heat cycle (DHA → VHF → DHA).
Dihydroazulene (DHA)/vinylheptafulvene (VHF) photo-/thermoswitch.
Bromination–elimination protocol for