Tellurenylation

The treatment of LiN(SiMc3)2 with aryl tellurenyl iodides gives stable Ai,iV -bis(trimethylsilyl)tellurenamides that react with acetylenes to give acetylenyl tellurides (Eq. 2.4). 

Appreciably higher is the synthetic potential of the methods based on the use of such precursors as (3-bromotellurenylvinylaldehydes 5 and (3-methyldibromotel-lurovinylaldehydes 6 [97DOK(357)504], By bubbling ammonia through a benzene solution of tellurenyl bromide 5,4,5-tetramethyleneisotellurazole Ig was prepared in 70% yield. 

Type 5 tellurenyl bromides are not easily accessible. They were prepared by refluxing an acetic acid solution of tellurium dibromides 6 in the presence of catalytic amounts of HBr [96ZOK1434 97JOM(536-537)233]. The reaction is not easily reproducible, affording the tellurenyl bromides in rather low yields. 

Benzo-l,2,3-telluradiazolium perchlorate 87 is the only compound known so far containing a 1,2,3-telluradiazole ring. It was obtained in 65% yield by reaction of the tellurenyl chloride 88 with silver perchlorate (88KGS1426). 

This group of compounds is represented by A-methyl-2,5-diphenyl-l-aza-6-oxa-6fl-tellurapentalene 94 which was prepared in low yield (11%) by coupling an imidoyl chloride 95 with a tellurenyl chloride 96 in acetonitrile solution containing 2,6-lutidine (87MI2). 

Association of Sulfenyl, Selenenyl and Tellurenyl Halides with Chelating Substituents... 

Organotellurium(II) compounds can also contain a three-center, four-electron bond as shown for 39 to 42 in Fig. 19. Typically, these molecules contain an odd number ligands around the central atom and an electronegative atom helps to stabilize a tellurenyl halide or selenenyl halide bond through chelation to form a four, five, or six membered ring. " Such molecules are described as lO-Te-3 and lO-Se-3... 

Halogenated derivatives of tellurium in the oxidation state +2, namely tellurenyl halides, are unfamiliar compounds compared to the well-known selenium analogues. 

These compounds are in principle easily accessible by the controlled halogenolysis of the parent ditellurides. However, the first compound obtained in 1959, 2-naphthyl-tellurenyl iodide, remained for a long time the only stable representative of this class until the preparation of other members of this class by a successful use of the same method." ... 

Tellurophosphoranes, obtained through a transylidation reaction between tellurenyl halides and phosphoranes, react with aldehydes to give the expected vinylic tellurides as an E Z isomeric mixture (method a). One other methodology involves the treatment of equimolar amounts of phenyl tellurenyl bromide and phosphonium salts with t-BuOK followed by an aldehyde (method b). Under these lithium-salt-free conditions, (Z)-vinylic tellurides are the main products. ... 

The sequential treatment of 1-alkynes with n-BuLi, trialkyl borane and a tellurenyl bromide reaches the (Z)-borosubstituted vinyl telluride which is easily hydrolyzed to the disubstituted vinyl tellurides. The reaction proceeds with high regio- and stereocontrol. ... 

The following scheme illustrates the different regio- and stereochemical outcomes of the sequential addition of the Schwartz reagent (Cp2Zr(H)Cl) and butyl tellurenyl bromide to acetylenic selenides. ... 

The alkyne hydrozirconation protocol was also applied to acetylenic tellurides furnishing the zirconated vinyl tellnrides in cis fashion and high regioselectivity. Subsequent treatment with tellurenyl halides affords telluro ketene acetals with total retention of configuration. ... 

Following the precedent methodologies, telluro(stannyl) ketene acetals are achieved by the hydrozirconation of stannyl acetylenes and successive reactions with butyl tellurenyl... 

From alkynyl Grignard and lithium compounds and organyl tellurenyl halides... 

A one-pot reaction of phenylacetylene with a dialkyl ditelluride and an alkyl iodide under phase transfer catalysis (method a). The same product can be obtained by using the tellurenyl iodide prepared in situ (method b). ... 

The reaction is regioselective and sterospecific the tellurium moiety is added exclusively to the terminal carbon of terminal aUcenes, and only frany-adducts are obtained with cyclohexene. The reaction may proceed through the tellurenylation of the olefin (in a rapid equilibrium as demonstrated in separate experiments), forming a telluronium intermediate which is then methanolysed. 

Mono- and bis-tellurenyl ferrocenes are achieved respectively by treatment of lithiated fer-rocenes with butyltellurenyl bromide (route a) or with dibutyl ditelluride (route b). Mono tellurenyl ferrocene is also obtained in a two-step procedure by treating lithiated ferrocene with Te to give the ditelluride followed by reductive alkylation (route c). - ... 

This conversion involves the intermediacy of an iodonium ion which suffers the attack of the iodide anion, promoting cycUzation through the tellurenyl iodide (pathway a) or by the direct pathway b. 

The intramolecular condensation of o-acetylphenyl tellurenyl bromide in basic medium gives 3-oxo-2,3-dihydro benzotellurophene. ... 

The 4-0X0-477-1-benzoteUurins have also been prepared by the cyclization of 2-(3-dimethylamino propenoyl)-phenyl tellurenyl bromide by heating with hypophosphorous acid in pyridine. ... 

When such groups are not present, the organotellurium halide cannot be isolated. In these cases, aryl, alkenyl, and alkyl tellurenyl halides, usually bromides and iodides, are prepared and used in situ. ... 

R—Te—O —C103 aryl tellurium perchlorate tellurenyl perchlorate... 

Organo tellurium halides, also named organo tellurenyl halides, are in principle easily accessible through controlled halogenolysis of diorgano ditellurium compounds. However, 2-naphthyl tellurium iodide, prepared in 19592 from bis[2-naphthyl] ditellurium and iodine, remained the only compound of this type until 1971/72, when a series of ortho-carbonyl substituted phenyl tellurium halides were synthesized3-4. Aryl tellurium halides without substituents in the ortho-position to tellurium were isolated and characterized in 1975s. 

Bis[2-tellurophene]iodonium chloride and sodium nitrite heated in DMF produced 2-iodotellurophene and bis[2-tellurenyl] tellurium but not 2-nitrotellurophene. Without sodium nitrite, 2-iodotellurophene was also formed but in low yields3. 

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