Thiobenzaldehyde dianions

The case of thiobenzaldehyde dianions, which are available from benzylthiol and two equivalents of n-butyllithium-TMEDA complex, merits further comment since alkylation or allylation of these species occurs selectively at the carbanionic site and then a second alkylation can be carried out on the thiolate group (Scheme 16, entry a). ... 

Metal Complexes.—Minoura and Tsuboi have studied the reactivity of thiobenzophenone towards alkali metals. When dissolved in THF under an atmosphere of nitrogen, the thioketone reacted with one equivalent of alkali metal to form the rather unreactive radical anion (72). With more than two equivalents of alkali metal, however, the very reactive dianion complex (73) was formed according to the equilibrium (72) -I- Na (73). The structure of (73) was established mainly on the basis of the reactions with electrophilic reagents. Thus the reactivity of (73) closely parallels that of the thiobenzaldehyde dianion (12). ... 

Another route to thioaldehyde and thioketone complexes uses the tungstate [W(CO)5SH] as the precursor. When [W(CO)5SH] was treated with ketones in the presence of trifluoroacetic acid, thioketone complexes [W(CO)5 S = C(R1)R2 ] were formed. Analogously, thiobenzaldehyde complexes were obtained from [W(CO)sSH]- and benzaldehydes bearing electron-releasing para substituents. Benzaldehyde, benzaldehydes with electron-withdrawing substituents, and aliphatic aldehydes did not react. Presumably, the binuclear dianion [p,-S W(CO)5 2]2 is an intermediate in the reaction, as on acidification of a mixture of [ju,-S W(CO)5 2]2 and p-N, A -dimethylaminobenzaldehyde the thioaldehyde complex [W(CO)5 S = C(C6H4NMe2-p)H ] is formed.143... 

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