TY - JOUR
T1 - Syntheses of donor-acceptor-functionalized dihydroazulenes
AU - Broman, Søren Lindbæk
AU - Jevric, Martyn
AU - Bond, Andrew
AU - Nielsen, Mogens Brøndsted
PY - 2014/1/3
Y1 - 2014/1/3
N2 - The dihydroazulene (DHA)/vinylheptafulvene (VHF) photo/thermoswitch has been of interest for use in molecular electronics and advanced materials. The switching between the two isomers has previously been found to depend strongly on the presence of donor and acceptor groups. The fine-tuning of optical and switching properties relies on ready access to new derivatives via efficient synthetic protocols. The central DHA core is conveniently prepared in a four-step synthesis starting from acetophenone and tropylium substrates. Here, the outcome of this reaction as a function of the nature of the substituent group on the phenyl unit of acetophenone is investigated in detail. A wide variety of functional groups (nitro, cyano, halo, alkyl, amido, and thioether) was tolerated, and the route provided access to a large selection of substituted DHA derivatives (position 2 of DHA). These compounds were investigated for their ability to undergo subsequent functionalization in the seven-membered ring by a regioselective bromination–elimination protocol, introducing a bromo substituent at position 7. Halo-substituted DHAs were subjected to palladium-catalyzed cyanation, Sonogashira, Cadiot–Chodkiewicz, and Suzuki couplings and for the latter reaction; optimized conditions were developed by varying the palladium catalyst. In general, our focus was on reducing the formation of fully unsaturated azulene byproducts.
AB - The dihydroazulene (DHA)/vinylheptafulvene (VHF) photo/thermoswitch has been of interest for use in molecular electronics and advanced materials. The switching between the two isomers has previously been found to depend strongly on the presence of donor and acceptor groups. The fine-tuning of optical and switching properties relies on ready access to new derivatives via efficient synthetic protocols. The central DHA core is conveniently prepared in a four-step synthesis starting from acetophenone and tropylium substrates. Here, the outcome of this reaction as a function of the nature of the substituent group on the phenyl unit of acetophenone is investigated in detail. A wide variety of functional groups (nitro, cyano, halo, alkyl, amido, and thioether) was tolerated, and the route provided access to a large selection of substituted DHA derivatives (position 2 of DHA). These compounds were investigated for their ability to undergo subsequent functionalization in the seven-membered ring by a regioselective bromination–elimination protocol, introducing a bromo substituent at position 7. Halo-substituted DHAs were subjected to palladium-catalyzed cyanation, Sonogashira, Cadiot–Chodkiewicz, and Suzuki couplings and for the latter reaction; optimized conditions were developed by varying the palladium catalyst. In general, our focus was on reducing the formation of fully unsaturated azulene byproducts.
U2 - 10.1021/jo4020326
DO - 10.1021/jo4020326
M3 - Journal article
C2 - 24313926
SN - 0022-3263
VL - 79
SP - 41
EP - 64
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 1
ER -