Azulenium chemistry: towards new derivatives of photochromic dihydroazulenes

Organic & Biomolecular Chemistry
Anne Ugleholdt PetersenMogens Brøndsted Nielsen

Abstract

Here we present the preparation of a selection of azulenium ions by hydride abstraction from photochromic 1,8a-dihydroazulenes (1,8a-DHAs) incorporating two cyano groups at C-1. The reactivity of the electrophilic tropylium ring of these molecules towards lithium triisopropylsilylacetylide was investigated. The position of attack by the nucleophile depended on the substitution pattern of the azulenium cation but was in general found to occur preferentially at positions C-4, C-5, and C-6, and to a minor extent at positions C-7 and C-8. The outcome was a mixture of non-photochromic, regioisomeric DHAs. One of these compounds containing the ethynyl substituent at position C-4 was partly tautomerized to the photochromic 1,8a-dihydroazulene, which was isolated and its switching properties were investigated by UV-Vis absorption spectroscopy. Upon irradiation, it undergoes a ring-opening reaction to form a vinylheptafulvene (VHF), which in turn returns to the original DHA. The half-life of this reaction was significantly smaller than for a derivative with the alkynyl substituent placed at C-7. This fast switching behavior was according to the calculations explained by an enhancement in the stability of the reactive s-cis conformer of ...Continue Reading

References

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Aug 10, 2011·Organic & Biomolecular Chemistry·Louise SkovMogens Brøndsted Nielsen
Dec 14, 2011·Organic Letters·Søren Lindbæk BromanMogens Brøndsted Nielsen
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Apr 8, 2015·Chemistry : a European Journal·Martina CacciariniMogens Brøndsted Nielsen

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Citations

Feb 15, 2017·Chemistry : a European Journal·Anne Ugleholdt PetersenMogens Brøndsted Nielsen
Jun 3, 2016·Chemistry : a European Journal·Alexandru VlasceanuMogens Broendsted Nielsen
Feb 28, 2018·Physical Chemistry Chemical Physics : PCCP·Nicolai ReeKurt V Mikkelsen
May 19, 2018·Chemistry : a European Journal·Demelza Josephine Marion LyonsThanh Vinh Nguyen
Nov 6, 2018·Chemistry : a European Journal·Ieva LiepuoniutePanče Naumov
Mar 5, 2021·Organic & Biomolecular Chemistry·Georgia E WilliamsSimon E Lewis

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