ELSEVIER Synthetic Metals 103 (1999) 2344-2347 Synthesis of Novel &-Based Acceptor Dyads (AI-AZ) from Sultines Beatriz IlIescas, Nazario Martin, Ignacio PBrez and CargosSeoane Depatimento de Quimica Orginica, Facuhd de Quimica. Universidad Complutense, E-28040 Madrid (Spain) Abstract A new &-based acceptor dyad has been prepared from 4,5(1,4-dimethoxybenzo)-3,6diiydro-1,2-oxathiin-2-oxide and C,. The first electron in the reduction process forms the radical-anion of the quinone moiety and the second electron is located on the Cm cage. Keywords: Semi-empirical models and model calculations, electrochemical methods, fullerene and derivatives. The chemical behavior of fullerene C6a is characterized by the absence of hydrogens on its skeleton and, therefore, exohedral functionalization of Cm has been mainly achieved by means of addition reactions.’ In this regard, Diels-Alder and 1,3-dipolar cycloadditions have been successfully used and a wide variety of different cycloadducts have been described.* o- Quinodimethanes have been reported to form thermally stable cycloadducts due to the stabilization provided by the generated aromatic ring, thus avoiding the cycloreversion to the starting materials.3 From the different methods available in the literature for the generation of o-quinodimethane (1)4 (Scheme 1). the use of 4,5-benzo-3,6-dihydro-1,2-oxathiin-2-oxide (sultine) (7)’ presents some advantages, since 1 is readily generated by SO1 extrusion under mild conditions (-80 “C) and no organic or inorganic by-products are formed. 0-c :I ; 4 Scheme 1 We have reported the first [6O]fullerene cycloadducts &om sultines as a very convenient method for the chemical modification of C60.6 More recently, we have used this synthetic approach for the preparation of differently substituted cycloadducts which are subsequently transformed into a p- benzoquinone moiety (9).7ax Cycloadducts 9 show the lowest activation energy barriers found for a boat-to-boat cyclohexene ring inversion in C&- based Diels-Alder cycloadducts.’ The electrochemical properties of compounds 9 were studied by cyclic voltammetry (CV) measurements and theoretical calculations. Depending upon the electronic nature of the substituents on the p benzoquinone ring, it is possible to address the attachment of the tirst electron in the reduction process either to the Cso core or to the organic addend.’ 9a: R= H 9b:R=Br 9c: R = -(CH=CH) T Further attempts to transform compounds 9 into the corresponding teuacyano-pquinodimethane (TCNQ) an& dicyano-pquinonediimine (DCNQI) were unsuccessf%l. The lower reactivity of other functional groups has been previously observed and it has been accounted for by the close proximity to the Cc0 surface.g In order to confirm this hypothesis and to gain some understanding of the experimental fmdings, we have carried out a multistep synthesis to afford to the novel compound 18 in which the p-benzoquinone ring is separated from the Cm cage through an additional benzene ring in comparison to compounds 9, In addition, compound 18 presents two electron- acceptor moieties covalently connected between them. In this regard, the design of novel modified fullerenes exhibiting better electron-acceptor properties than Cm has been scarcely studied in spite of the interest of these compounds for the development of specific optical and electronic applications. Only recently, some organofullerenes showing more positive reduction potentials than the parent [6O]fullerene have been reported”*” The synthesis of 18 is shown in Scheme 2. 1,4- Dimethoxy-6,7dimethylnaphthalene (13) was prepared ffom p benzoquinone by [4+21 cycloaddition with 23 dimethylbutadiene, followed by methyla$ion and subsequent oxidation with DDQ. Reaction of 13 with bromine and, in a further step, with NBS affords the tetrabromine derivative 15. Sultine 16 was prepared from 15 by reaction with sodium hydroxymethanesulfinate (rongahte) in the presence of catalytic amount of TBAB.’ Finally, reaction of sultine 16 with Cm yields cycloadduct 17 which is transformed into the p- benzoquinone derivative in one step by treatment with boron tribromide (see experimental). The redox properties of cycloaddu!t 18 were studied by CV in toluene:acetonitrile solution and the data are collected in the Table, together with other related compounds prepared in our group for comparison purposes. 0379~6779/99/$ - see front matter 0 1999 Elsevier Science S.A. All rights reserved. PII: SO379-6779(98)00293-S