Nicola Petragnani

Aryl tellurium trihalides—I

Abstract New aryl tellurium trichlorides have been prepared. A method for synthesizing aryl tellurium tribromides and triiodides based on the halogenolysis of the corresponding ditellurides is presented. Thiophenoxtellurine was obtained from o-thiophenoxyphenyltellurium trichloride.

The reaction of selenenyl halides with wittig reagents

Abstract The transylidation reactions of PhSeBr with two equivalents of an alkylidene-triphenylphosphorane give selenophosphoranes, Ph3P=CRSePh. These also can be obtained by treating the corresponding selenophosphonium salts, prepared by quarternization of triphenylphosphine with PhSeCHRBr, with n-BuLi. The selenophosphoranes react with aldehydes in situ (Wittig reaction) to give the expected vinylic selenides in good yields. The stereochemistry of the reactions is discussed.

The reaction of selenophosphonates with carbonyl compounds. Vinylic selenides

Selenophosphonates of the general formula (EtO)2P(O)CHRSePh were prepared and their reactions with aldehydes and ketones investigated. The products formed are vinylic selenides having predominantly the E configuration. Hydrolytic cleavage of these products gives the corresponding ketones.

Synthesis of vinylic tellurides

Synthetic routes to vinylic tellurides employing nucleophilic and electrophilic tellurium species are described. Reaction of vinyl Grignard reagents with organotellurenyl bromides leads to vinylic tellurides (p-CH3OC6H4TeCHCHC6H5, p-CH3OC6H4Te(CH3)CCH2, n-C4H9TeCHCH2) in 71–86% yield; vinyltellurenyl iodides react with Grignard reagents to give vinylic tellurides (p-CH3OC6H4Te(CH3)CCH2, p-CH3OC6H4TeCH2, n-C4H9TeCHCH2) in 64–71% yield; trans-β-Bromostyrene react with p-CH3OC6H4Te− and n-C4H9Te− to give vinylic tellurides of trans configuration (p-CH3OC6H4TeCHCHC6H5, n-C4H9TeCHCHC6H5) in 86 and 83% yield, respectively; reaction of vinyl Grignard reagents with elemental tellurium followed by alkylation with n-bromobutane gives vinylic tellurides (n-C4H9Te(CH3)CCH2, n-C4H9TeCHCH2, n-C4H9TeCHCHCH3, n-C4H9TeCHCHC6H5) in 73–79% yield; divinyl ditellurides (C6H5CHCHTe)2, (CH3CHCHTe)2, (CH2CHTe)2, (CH2C(CH3)Te2) were prepared in 58–67% yield by reaction of vinyl Grignard reagents with elemental tellurium followed by air oxidation; divinyl ditellurides react with formamidinesulfinic acid in 50% sodium hydroxide under phase transfer conditions in the presence of n-C4H9Br to give vinylic tellurides (n-C4H9TeCHCHC6H5, n-C4H9TeCHCHCH3, n-C4H9Te(CH3)CCH2, n-C4H9TeCHCH2) in 81–86% yield; addition of n-C4H9Te− to acetylenes gives vinylic tellurides of cis-configuration (n-C4H9TeCHCHC6H5, n-C4H9CHCHCH2NCH2CH2OCH2CH2, n-C4H9TeCHCHCH2OCHOCH2-CH2CH2CH2CH2) in 78–93% yield.

Synthesis of unsymmetrical tellurides and selenaditellurides

Abstract Unsymmetrical tellurides may be prepared by the reaction of arenetellurenyl halides, generated in situ, with Grignard reagents. Selenaditellurides, RTeSeR, are prepared from the reaction of arenetellurenyl halides with ArSeMgBr.

Addition of tellurium tetrabromides and alkyl and aryl tellurium tribromides to terminal acetylenes

Abstract The addition of tellurium tetrabromides and alkyl and aryl tellurium tribromides to terminal acetylenes gives rise to thecorresponding bis(b-bromovinyl)tellurium dibromides and (b-bromovinyl)organyl tellurium dibromides which, by treatment withNaBH 4 , leads to formation of the reduced tellurides.

Cyclofunctionalization with Aryltellurium Trichlorides

Abstract Some years ago one of us1 found that diphenylallylacetic acid (I) reacts with arylselenenyl halides, naphtyl tellurenyl iodide, tellurium tetrachloride as well as with aryltellurium trichlorides to give the corresponding lactones (II) (Eqn. 1).

Preparation of the Principal Classes of Organic Tellurium Compounds

This chapter discusses diorganyl tellurides and ditellurides, organyltellurium trichlorides and diorganyltellurium dichlorides, which were the first classes of compounds investigated at the beginning of tellurium (Te) organic chemistry. Diorganyl tellurides, compounds with two organic groups linked to a Te atom, constitute the most abundant and familiar class of organic Te compounds. The organic groups of the most differentiated types can be identical or different, giving rise to symmetrical or unsymmetrical tellurides. The main routes to symmetrical diorganyl tellurides involve the direct reaction of nucleophilic telluride dianions with alkylating or arylating reagents. Otherwise, the electrophilic Te tetrahalides react with arylmagnesium reagents, giving diaryl tellurides. Diorganyl ditellurides are prepared by three routes: alkylation or arylation of the ditelluride dianion; oxidation of tellurolate anions; and reduction of the corresponding organyltellurium trichlorides. Organyltellurium trichlorides and diorganyltellurium dichlorides are prepared starting from the electrophilic tellurium tetrachloride by (1) condensation reactions with active methylene compounds; (2) addition to a C=C bond; (3) electrophilic substitution in aromatic hydrocarbons; and (4) reaction with organomercury chlorides. This chapter explores the preparation of principal classes of organic Te compounds in detail.

New anionic species of tellurium(IV)

Abstract Tetrahaloaryltellurates(IV) were prepared by refluxing aryltellurium trihalides with phosphonium, tropylium and telluronium halides in CHCl 3 . These compounds, which contain the ArTeX − 4 anion, may be also prepared from aryltellurium trihalides and aqueous halogen hydride solutions. The phosphonium derivatives can be considered as potential precursors of tellurophosphoranes for Wittig reactions. Halogen exchange reactions allow the interconversion of the complex anions. The ionic nature of the compounds is supported by ion exchange reactions utilizing ion exchange resins, and by conductance measurements. Far infrared and Raman spectral data suggest a square pyramidal configuration for the ArTeX − 4 anions.

Cyclofunctionalization of unsaturated alcohols with aryltellurium trihalides

Abstract The reaction of unsaturated alcohols with aryltellurium trihalides leads to cyclic ethers bearing an aryldihalotelluro group in the β position, in high yields. Reduction of the tellurium-halogen bond with thiourea dioxide gives the corresponding tellurides in excellent yields.