Tetrathiafulvalene lithiation

In the course of exploring new synthetic routes to extended tetrathiafulvalene (TTF) derivatives, lithiation of S,S-acetals, followed by reaction with CS2 and PhCOCl, gave a-dithiomethylenes, which are possible versatile intermediates to extended TTFs. 1,2,3,5,6-Pentathiepanes 86 (Figure 25) were prepared from these intermediates <1995MI1>. 

Tetrathiafulvalene was lithiated in tetrahydrofuran at — 78= with four equivalents of lithio diisopropylamide to the tetralithiotetrathiafulvalene and with two equivalents to the dilithiotetrathiafulvalene. The lithiotetrathiafulvalines reacted with tellurium to give the tetrathiafulvalenetetra- or -ditellurolates5. 

The chemistry of TTF derivatives has only recently undergone major developments. The lithiation of tetrathiafulvalenes (Section II.B.3) undoubtedly constitutes the most significant development, because the met-allated species formed give rise to a wealth of new derivatives (Section II.C.6), many of which bear functional groups that are amenable to further synthetic elaboration (Section II.C). In contrast, very few examples of the reactions of tetrathiafulvalenes with either electrophiles (Section II. B. 2) or radicals (Section II.B.4) are known, and reports on [2 + 2]- and [4 + 21-cycloadditions of TTF are scarce (Sections II.B.l and II.B.5). Thus, the chemistry of tetrathiafulvalenes is dominated by the introduction and modification of substituents, whereas investigation of the reactivity of the ring atoms is relatively undeveloped. 

Since then, other tetrathiafulvalene derivatives have been lithiated, the majority of which are methyl-substituted [9 (79JOC1476 92BSB741),... 

Tetrathiafulvalene and simple derivatives thereof have been routinely lithiated with BuLi or LDA in either Et20 or THF. Although all of these systems seem to work well, LDA/Et20 has proved to be the most satisfactory in the author s laboratory. Lithiation of 13, however, has usually been carried out with LDA/THF [91ZN(B)1269 93MI5],... 

The reactions of formaldehyde with lithiated tetrathiafulvalenes 8 (79JOC1476) and 16 (88MI3) lead to the corresponding alcohols (Scheme 48). It is worth noting that a much improved synthesis of 27 has recently been described (94S489). 

The formation of TTF—Te bonds is carried out by reacting lithiated tetrathiafulvalenes with elemental tellurium. Two very surprising reactions that tetralithiated TTF undergoes have been described (88TL6177 92CC1048) (Scheme 58). A detailed structural and electronic study of these two donors has recently been reported (93CM1199). 

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