Organotellurium compounds, reactions

Several new types of Ge-O-bonded species have appeared and some new methods for the formation of such bonds have been described. Germoxanes can be obtained via reaction of triorganobromogermanes with oxygen in the presence of organotellurium compounds (Equation (127)).164 The germapropadiene 4 reacts with alcohols to provide alkoxides 70 (Equation (128)) or benzaldehyde to yield a 1,2-oxagermetane 71 via a [2 + 2]-addition (Equation (129)), which exhibits unusual thermal stability for an unencumbered oxagermetane.16... 

Organochalcogen(II) compounds, 100-102 Organochalcogen(IV) compounds, 100-102 Organoselenium compounds dehalogenation reactions, 96 electrochemical reduction, 113-117 haloperoxidase-like activity, 108-113 with odd number of ligands, 100-102 one-electron oxidation, 117-118 oxidation of thiols, 102-106 redox reactions, 79-80 thioperoxidase-like activity, 108-113 Organotellurium compounds... 

Reaction of organotellurium compounds with quinones (typical procedure, 2-benzyl-l, 4-benzoquinone) A solution of benzyl p-methylphenyl telluride (111 mg, 0.36 mmol) and 1,4-benzoquinone (78.0 mg, 0.72 mmol) in benzene (0.6 mL) in a Pyrex tube was irradiated with a 200 W high-pressure mercury lamp at 100°C for 1 h. After the solvent was removed under reduced pressure, the crude mixture was purified by flash chromatography (silica gel 6.4 g elution with 5% ethyl acetate in hexane) to give the product in 57% yield. 

An alternative to reductive radical cyclization procedures is the use of group transfer methods. A novel group transfer cyclization reaction involving an organotellurium compound 47 has been described [95CC2515]. The bicyclic product 48 is formed as a 2 1 mixture of isomers at the terminus. 

This class of organotellurium compounds is an important source of nucleophilic (Sections 9.13.3.1 and 9.13.3.2) or electrophilic (Sections 9.13.4.2.4 and 9.13.4.3) tellurium species. Diorganoditellurides can also behave as electrophiles, but in such cases normally one organotellurium group is lost. In this way, the corresponding organotellurium halides (Section 9.13.4.3) are prepared as source of electrophilic tellurium. In the past, the title compounds were prepared mainly by reduction of aryltellurium trihalides, in some cases under drastic reaction conditions5 9 11 12 (Scheme 11). 

Since the publication of the chapter Tellurium in the second edition of this encyclopedia,12 a number of methods to transform organotellurium compounds into tellurium-free reactive organometallics and the use of such species in stereoselective carbon-carbon bond formation have been developed. Coupling reactions of organotellurium... 

The reactions of organotellurium compound with organolithium compounds give the ate complex as shown in eq. (3.34). 

Finally, ultrasound has been used in the preparation of a variety of organoselenium and organotellurium compounds by reaction of alkyl halides, tosylates, mesylates and epoxides with the phenylselenium anion [107] and... 

Tin Hydride-Mediated Reaction Allyltin Method Photochemical Fragmentation of Barton Esters Direct Photolysis of Cobaloximes Direct Photolysis of Organotellurium Compounds Miscellaneous... 

---