Preparation and chemistry of new unsymmetrically substituted tetrachalcogenofulvalenes bearing CN(CH2)2X and HO(CH2)2X groups (X = S or Se)

Abstract

Several unsymmetrically substituted TTFs bearing the S(CH2)2CN protecting group have been prepared by standard cross coupling in triethyl phosphite from the key intermediate 4,5-bis(2′-cyanoethylsulfanyl)1,3-dithiol-2-one 1 and an appropriate 1,3-dichalcogenole-2-chalcogenone, 2–8. TTFs 10, 11 and 12 of type I have been obtained in satisfactory yields (30–60%) and those (13,14) of type II in low yields (10 and 19%) as a result of differences in the reactivity of the species involved.Pseudo-Wittig condensations from the key triphenylphosphonium salt 15 have allowed considerable improvement in the synthesis of 13 (70% yield) and 14 (57% yield).The diselena analogue of 1, 21 has also been obtained. Its derivative 22, a new tetrakis(alkylselena) functionalised TTF, has been isolated in fair yield (69%). Its deprotection in a basic medium followed by a subsequent alkylation has led to BEDSe-TTF 23 (40%). Finally, the same sequence of deprotectionrealkylation carried out from unsymmetric species 10 and 12 has successfully been used in a high yield preparation of the corresponding new functionalised TTFs bearing two hydroxyethyl groups.