Aryltellurolates

Recently, a one-pot method for preparation of 2-aryl-1,5-benzotelluroazepines 60 has been developed based on the reaction of sodium 2-aminophenyltellurolate [from di(o-aminophenyl) ditelluride) with arylpropargyl aldehydes (99MI1). Considering the high affinity of supemucleophilic aryltellurolate anions to a triple bond, one may assume that at the first stage of this reaction arylvinyl tellurides 61 are formed. Cyclization of 61 spontaneously or on silica gel in a chromatographic column forms the heterocycles 60. 

Organyl tellurols are very unstable compounds owing to their extreme sensitivity to oxygen, giving the corresponding ditellurides. The first short-chain alkyltellurols (C1-C4) have been isolated as yellow liquids with an obnoxious odour, from the reaction of aluminium telluride and hydrogen telluride, respectively, with alcohols and aUcyl bromides. Aryltellurols seem not to have been isolated. As shown in Sections 3.1.3.2 and 3.2.2, aryl tellurolates are... 

Starting materials for the preparation of aryl tellurides and diaryl ditellurides and, consequently, aryltellurols find wide use in the manipulation of several organic functionalities. 

Alkyl- and aryltellurols generated in situ by the well-established reduction of ditellurides with NaBH /EtOH add to terminal acetylenes, giving (Z)-vinylic tellurides. "" ... 

Telluroesters have also been employed as starting materials in teUuro vinylation reactions. Thus, by treatment of telluroesters with aryl propiolates in the presence of KjCOj, (Z)-/(-acyltellurocinnamates are formed in high yields. This procedure involves the addition of potassium aryltellurolate anions derived from the telluroesters. " ... 

The reduction of azo compounds to hydrazo compounds is also achieved by means of aryltellurols or sodium hydrogen telluride. The last reagent (generated from NaBH4 and... 

In accordance with the following scheme the hydroxyaldehyde A was submitted to a Wittig olefmation followed by the mesylation of the hydroxyl group to give the a,)3-unsat-urated compound B which was in turn converted into the telluride C by treatment with the appropriate aryltellurolate. Irradiation of C in the presence of iV-acetoxy-2-thiopyridone gave rise to the cyclic compound D. 

At present there are few examples of isolable, well-characterized sources of tellurolate anions (RTe-).1 Although insertion of elemental tellurium into reactive metal-carbon bonds has been known for many years, the resulting solutions contain a mixture of compounds in addition to the RTe- species of interest.2 Alkali metal phenyltellurolate salts, prepared via metal reduction of diphenyl ditelluride in liquid ammonia, were first isolated by Klar and co-workers.3 More recently Lange and Du Mont reported the synthesis of the bulky aryl tellurolate (THF)3Li[Te(2,4,6-f-Bu3C6H2)],4 and Sladky described the in situ formation of a bulky alkyl tellurolate via reaction of tellurium with LiC(SiMe3)3.5 Acidification of aryltellurolate anions affords thermally sensitive tellurols (RTeH) that are stable only below room temperature.6... 

It is also relevant to record that several iron-carbonyl complexes with bridging, and in one case terminal, aryltellurol ligands have been prepared by reaction of Fe(CO)5, Fe(CO)12 or [ji-CpFe(CO)2]2 with diaryl ditellurides and which, together with complexes containing other transition metal carbonyls, e.g, ruthenium, osmium and manganese, provide a substantial number of interesting compounds.2... 

Treatment of alkali metal alkyl or aryltellurolates (Sections) with alkyl halides, aryl halides, alkenes, or alkynes have been nsed to prepare unsymmetrical tellurides, as exemplified by the reaction of sodium phenyl teUurolate or paramethylphenyl tellnrolate with PhC CHCOPh. ... 

The reaction of hthium or sodium aryltellurolate with alkynyl phenyl iodonium triflates" or tosylates. ... 

Alkynylphenyl tellurides from aryltellurolates and alkynyliodonium salts (general procedure) To a stirred solution of PhLi in Et20/cyclohexane at room temperature under N2, tellurium powder was added and the solution was stirred for 1 h. The appropriate iodonium triflate was added and the solution was stirred for 2 h. The product was eluted through a small portion of silica gel with CH3CN and the volume was reduced in vacuo followed by purification via radial chromatography. 

Triphenyltelluronium salts react with sodium aryltellurolate to afford the ligand coupling products. Metastable crystals of the ditellurium intermediate (74) have even be isolated. Their thermal decomposition led to the ligand coupling products. ... 

Unlike the chemistry of alkyltellurolate-silver complexes, which must usually be formed at low temperatures to avoid the precipitation of amorphous solids and of which we have isolated relatively few structural types vide supra), the chemistry of aryltellurolate silver complexes is rich and varied in respect of the polynuclear frameworks formed. The reagents can also be classified as gentler in that reactions between the phosphine-solubilized metal salt and the silylated chalcogens can often be performed at room temperature to yield medium sized polynuclear complexes. 

When BuLi was added to aryltellurol esters in THF/Et20 at low temperatures in the presence of pinacolone as an electrophile, a-hydroxy ketones 90 were obtained in high yields via aroyllithiun 89 together with dibutyl telluride (Eq.66) [124]. 

Although the synthesis of butylteUurolate-silver complexes requires low temperatures in order to avoid the precipitation of amorphous solids, and relatively few structural types of these compounds have been isolated (see above), the chemistry of phenyltellurolate-silver complexes from PhTeSiMc3 and AgCl is rich and varied with respect to the polynuclear frameworks formed. These aryltellurolate reagents can also... 

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