Synthetic Metals 160 (2010) 1797–1799 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Short communication Synthesis of brominated tetrathiafulvalenes via phosphite-mediated cross-coupling Antonio Alberola a , Concha Bosch-Navarro b , Pablo Gavi ˜ na b,∗ , Sergio Tatay b a Departamento de Química Física y Analítica, Universidad Jaime I, P.O. Box 224, 12080 Castellón, Spain b Instituto de Ciencia Molecular, Universidad de Valencia, C/Catedrático José Beltrán, 2, 46980, Paterna, Valencia, Spain article info Article history: Received 3 May 2010 Received in revised form 28 May 2010 Accepted 2 June 2010 Available online 2 July 2010 Keywords: Brominated tetrathiafulvalenes Lithiation Halogenation Phosphite cross-coupling abstract The synthesis of polybrominated tetrathiafulvalenes (TTF–Br n , 2–4) containing 2–4 bromine atoms via phosphite-mediated cross-coupling of bromo-substituted 1,3-dithiole-2-thiones and 1,3-dithiole-2-ones is reported. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Since the discovery of the first metallic charge transfer salts based on tetrathiafulvalene (TTF) [1], a great number of TTF deriva- tives have been synthesized. Amongst them, halogenated TTFs have attracted attention not only for their electronic proper- ties but also for the directing role played by the halogen atoms in determining their solid state structures and redox potentials [2–4]. These halogenated derivatives can also act as valuable starting materials in the synthesis of more elaborated deriva- tives. To date, several groups have reported the synthesis of bromo-TTF derivatives by lithiation of the parent TTF followed by halogenation; however product distributions and yields have proven to be strongly dependent on reaction conditions even in the simplest case of 2-bromotetrathiafulvalene (1) [4–8]. Lithiated TTF derivatives tend to disproportionate, even at low temper- ature, and consequently trapping these lithiated intermediates with electrophiles frequently yields mixtures of unreacted start- ing material and mono- and polysubstituted products [7,9]. In the case of lithiation of halogenated TTFs, additional difficulties are present due to the possibility of lithium–halogen exchange [7]. There are numerous routes to nonsymmetrically substituted TTFs [10,11], although coupling of two 1,3-dithiole-2-thione (or 2- one) half-units, usually in the presence of a trialkylphosphite is the ∗ Corresponding author. E-mail address: pablo.gavina@uv.es (P. Gavi ˜ na). most widespread. However, the number of examples is limited in the case of halogenated TTF derivatives [3,12,13]. Our need to reliably and selectively obtain these compounds prompted us to test this approach for the synthesis of the TTF–Br n family (n = 2–4) (Scheme 1). Here we describe the synthesis of brominated TTF derivatives 2–4 from appropriately bromo- substituted 1,3-dithiole-2-thiones and 1,3-dithiol-2-ones using a cross-coupling methodology. 2. Results and discussion The starting mono- and dibrominated derivatives 4-bromo- 1,3-dithiole-2-thione (6) and 4,5-dibromo-1,3-dithiole-2-thione (7) were obtained in good yields by direct reaction of vinylen- etrithiocarbonate with 1 equiv. and 3 equiv. of LDA followed by treatment with 1,2-dibromotetrachloroethane, as reported earlier [14]. Ketones 8–10 were synthesized in nearly quantitative yield from the respective thiones 5–7 by reaction with Hg(OAc) 2 in CHCl 3 /AcOH (Scheme 2). Since the difference in reactivity of both types of chalcogenone (dithiole-2-thione and dithiol-2-one) in a trialkylphosphite medium is generally difficult to predict [10,11], a systematic approach was adopted to determine the best coupling reactants and conditions. The synthesis of compound 2a was chosen as a model reaction. We first attempted the coupling of thione 5 with thione 7, in the presence of an excess of P(OEt) 3 in refluxing toluene. In this case, we were unable to isolate neither 2a nor any starting material from the mixture of reaction products. Equal result was observed when 0379-6779/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2010.06.001