From sodium ditelluride

Method G. ° A catalytic cycle is also involved in this method. Sodium thienyl tellurolate, generated from the ditelluride and NaBH4, attacks a bromine atom and the formed tel-lurenyl bromide reacts with another tellurolate molecule regenerating the starting ditelluride. 

Sodium ditelluride, prepared from the elements in dimethylformamide, reacted with 5,6,11,12-tetrachloronaphthacene2 and with 7,8-dichloro-l,2-diselenanaphthacene3 to produce the compounds I and II. Crystal and molecular structures for these compounds were determined2,4. 

Based on this unfortunate result, 119 was envisioned a synthesis of the elusive 1,6-epitelluro 119. Thus, the above sequence was repeated but with sodium ditelluride as the reagent the only product formed was that from a simple base-induced elimination, the alkene 118 <2005AJC188>. A very similar study has been published by an Indian... 

Olefins and allylic alcohols from alkyl or cycloalkyl bromides and from epoxides (general procedures The i-alkyl or cycloalkyl bromide is treated with sodium phenyl tellurolate (1 equiv from diphenyl ditelluride and NaBH, see Section 3.1.3.2). The crude telluride is purified by SiOj chromatography (elution with hexane) and converted into the corresponding dibromide by addition of bromine (1 equiv) in CCI4, at 0°C. Epoxides are converted into j8-hydroxylalkyl and )3-hydroxycycloalkyl phenyl tellurium dibromide by a similar procedure, except that the intermediate tellurides are chromatographed on SiOj using hexane/EtOAc (5 1) as the eluent. 

Dihydroacenaphtho[5,6-cfi(]-l,2-diselenole (65) was prepared from 5,6-dibromoacenaphthene via the dilithio derivative <80TL4565,88BCJ2013). The ditelluro compound (3), however, could not be prepared by this method but was synthesized by reaction of sodium ditelluride with 5,6-dichloro-acenaphthene in HMPA <88BCJ2013>. 

Phenylselenofluoration of acetylenes 359 (R = Pr or Bu) to give 360 is accomplished by the joint action of A-(phenylseleno)phthalimide and EtsN-SHF. Free-radical selenosulphonation of conjugated enynes by PhSeTos under photochemical conditions or in the presence of azoisobutyronitrile yields mixtures of stereoisomers, e.g. equation The action of / -methoxyphenyltellurium trichloride on terminal alkynes RC=CH (R = cyclohexyl, HOCH2 or Ar) results in cw-adducts 361 (Ar = -MeOC6H4) 48 Sodium benzenetellurolate, PhTeNa, formed in situ from diphenyl ditelluride and sodium borohy-... 

From fluorest nce X-ray measurements, the percentage of bromine present in the polymers was found to be less than 1% of that of tellurium, suggesting that the end groups are bromides [209]. Like any other polycondensation reactions, formation of cyclics also occurs along with that of the primer. For example, the reaction of n-butyldiiodide with sodium ditelluride results in the formation of the polymer along with the six-membered cydic ditelluride [234] ... 

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. 

Acidification of sodium phenylethynetellurolate produced red rhombic crystals with a melting point of208 -210° (from dimethylformamide). The structure of this compound was ascertained by X-ray diffractometry. The 1,2,4-tritellurolane is very likely formed by addition of telluroketene to the phenylethynyl ditelluride anion1 3. 

Disodium ditelluride can be prepared from tellurium and sodium in liquid ammonia, lithium triethylborohydride in THF, sodium borohydride in ethanol or THF" lithium or sodium in ethylenediamine , sodium hydride in DMF , hydrazine hydrate in aqueous sodium hydroxide , thiourea dioxide in DMF/THF/aqueous sodium hydroxide, and sodium formaldehyde sulfoxylate (Rongalite C) " in aqueous sodium hydroxide. The reducing agents compatible with organic solvents provide reaction media in which long-chain aliphatic halides are soluble. Such halides are insoluble in liquid ammonia, or aqueous media. 

The aldehyde was then converted to a carboxylic acid via a Pinnick oxidation. Further elaboration to generate acyl telluride 185 was achieved by initial activation of the acid as a mixed anhydride using isobutyl chloro-formate under basic conditions. Nucleophilic displacement with sodium phenyl telluride, generated in situ from borohydride reduction of diphenyl ditelluride, completed the transformation. With acyl telluride 185 in hand, nitrogen deprotection employing TFA, followed by a reductive amination with aldehyde 186 furnished alkyne 187, which was envisioned to be a substrate for radical cyclization (Scheme 19). 

Sodium telluride and ditelluride are readily generated in situ from Te by reduction with thiourea dioxide, and subsequent treatment with alkyl halide provides the corresponding dialkyl tellurides and ditellurides. E Thiourea dioxide and NaOH in 1 1 water/THF added to Te under N2, the mixture refluxed for 1 h, n-octyl halide and a little cetyltrimethylammonium bromide in THF added, and refluxing continued for 1 h - dioctyl telluride. Y 85%. The method is cheap, simple and does not require very dry conditions. F.e. and sym. ditellurides s. J.T.B. Ferreira et al., Synth. Commun. 19, 239-44 (1989) prepn. of Na2Te from ultra-pure Te-ingots/Na-naphthalenide, or from Te/Na and a little naphthalene, s. K.T. Higa, D.C. Harris, Organometallics 8, 1674-8 (1989). 

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