2,4,6,8-Tetracyanoazulene: A New Building Block for “Organic Metals”

Synthesis of Polycyano-Substituted Azulenes via Direct Oxidative Cyanation Reaction

“…The attempts at direct cyanation of unsubstituted azulene (1) (4 equiv of TEAC, in DMF, r.t.; then oxidation with DDQ at -78°C) did not give the desired cyano-compound; the only isolated product 2, was apparently formed via substitution of the CN group in DDQ by the azulene moiety (Scheme 1). Absence of the cyanation product is in agreement with the observation reported by Hafner et al 3 that azulene was insufficiently active as an electrophilic partner for the reaction with such a weak nucleophile as CNanion.…”

“…3 In our studies on nucleophilic substitution of hydrogen in electron-deficient arenes via vicarious nucleophilic substitution (VNS) 4 and oxidative nucleophilic substitution of hydrogen (ONSH) 5 we have found that anionic s H -adducts of carbanions and some other nucleophiles to azulene derivatives can be directly converted into corresponding substituted products via VNS and ONSH pathways. 6 Since earlier reports on 2,4,6,8-TCNA revealed its many interesting properties 3 we have attempted to elaborate the synthesis of other polycyanoazulenes using an approach developed in our laboratory -direct oxidation of anionic s H -adducts of CNanion to substituted azulenes. For the cyanation reaction we have used tetraethylammonium cyanide (Et 4 N + CN -, TEAC; Fluka) readily soluble in dichloromethane, chloroform, and other moderately polar, low boiling solvents.…”

A Novel Route to a Bromo‐Cyano‐Substituted Azulene and Its Exploitation in the Construction of an Acetylenic Scaffold

“…Cyano‐substituted azulenes have proven as good electron acceptors that may be employed in organic metals. Thus, Hafner and co‐workers3 showed that the electron donor tetrathiafulvalene forms a charge‐transfer complex with 2,4,6,8‐tetracyanoazulene ( 2 ). This compound was prepared from 2‐cyanoazulene ( 3 ) by nucleophilic substitution reactions in the seven‐membered ring, followed by hydrolysis and dehydrogenation steps.…”

The preparation of thiophene-S,S-dioxides and their role in organic electronics

“…Azulene has striking electronic properties. 33 The unique structure consists of an electrondeficient seven-membered ring fused to an electron-rich five-membered ring. Protonation of the five-membered ring leads to aromatization of the sevenmembered ring, a reversible process that completely changes the electronic properties of azulene.…”