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

Y1 - 2014

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

VL - 79

SP - 41

EP - 64

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

IS - 1

ER -