Azulene Functionalization by Iron-Mediated Addition to a Cyclohexadiene Scaffold

Synthesis of C3-functionalized indole derivatives via Brønsted acid-catalyzed regioselective arylation of 2-indolylmethanols with guaiazulene

The first Brønsted acid catalyzed method for the construction of guaiazulenyl C3-functionalized indole derivatives was established. The reactions proceeded smoothly at ambient temperature by used (±)-10-camphorsulfonic acid (CSA) as catalyst,...

Copper-Catalyzed 3-Positional Amination of 2-Azulenols with O-Benzoylhydroxylamines

A copper-catalyzed ortho-selective amination of 2-azulenols with O-benzoylhydroxylamines (RR'N-OBz) to synthesize ortho-aminoazulenols is reported. A wide range of functional groups on amines are compatible, furnishing the corresponding amino-azulene derivatives in moderate to good yields. The further synthetic elaboration using 3-amino-2-azulenols as starting materials is demonstrated.

C4-aldehyde of guaiazulene: synthesis and derivatisation

Guaiazulene is an alkyl-substituted azulene available from natural sources and is a much lower cost starting material for the synthesis of azulene derivatives than azulene itself. Here we report an approach for the selective functionalisation of guaiazulene which takes advantage of the acidity of the protons on the guaiazulene C4 methyl group. The aldehyde produced by this approach constitutes a building block for the construction of azulenes substituted on the seven-membered ring. Derivatives of this aldehyde synthesised by alkenylation, reduction and condensation are reported, and the halochromic properties of a subset of these derivatives have been studied.

Azulene-A Bright Core for Sensing and Imaging

Azulene is a hydrocarbon isomer of naphthalene known for its unusual colour and fluorescence properties. Through the harnessing of these properties, the literature has been enriched with a series of chemical sensors and dosimeters with distinct colorimetric and fluorescence responses. This review focuses specifically on the latter of these phenomena. The review is subdivided into two sections. Section one discusses turn-on fluorescent sensors employing azulene, for which the literature is dominated by examples of the unusual phenomenon of azulene protonation-dependent fluorescence. Section two focuses on fluorescent azulenes that have been used in the context of biological sensing and imaging. To aid the reader, the azulene skeleton is highlighted in blue in each compound.