Synthesis and properties of azulene-containing 1,3-dioxanes
Alexandru C. Razus,* Liviu Birzan, Liliana Cristian, and Victorita Tecuceanu
Institute of Organic Chemistry “C. D. Nenitzescu”of Romanian Academy, Spl. Independentei, 202B, PO Box 35-108, 060023 Bucharest, Romania
E-mail:
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Abstract
[1,3]Dioxane-4,6-diones with (azulen-1-yl)methylene attached to position 5 were obtained by condensation of azulene-1-carbaldehydes with Meldrum’s acid. The reaction was performed either neat or in absolute ethanol using a base as a catalyst. The involvement of the generated C=C bond either in electrophilic or radical reactions appears to be restricted. The advanced molecular polarization of the obtained products can account for the low reactivity of this bond. With the electrophilic reagents only the 3-position of azulenyl moiety was substituted. The azulene acylation with acetylsalicyloyl chloride occurred with rearrangement of the acyl chloride and, the formed products are 4H-1,3-benzodioxin-4-ones where azulen-1-yl moiety occupies the position 2 of the heterocyclic system.
Keywords: Azulene, [1,3]dioxane-4,6-dione, 4H-1,3-benzodioxin-4-ones, Meldrum’s acid
Introduction
The wide use of redox molecular receptors, for example in analytical chemistry,1 stimulated the interest on their synthesis and properties. The reported results showed that, generally, the structure of such compounds should contain three elements with specific functions: a C=C double bond which polymerizes on electrode, a chelating group and one with reversible redox property. The good redox property of the azulene compounds suggested us to use this system for the synthesis of molecular receptors. Due to the low stability of unsubstituted vinylazulenes,2 the C=C bond must be substituted with stabilizing groups, such as carboxyl or cyan.3 The group with chelating function can be attached to azulene before or after generation of the double bond. As part of our research in this field, we report here two classes of 1,3-dioxanes which are substituted with azulene-1-yl group, compounds that appear to be possible synthones for generation of redox molecular receptors.
