Bis-vinylic tellurides

Bis(trispyrazolylborate)titanium(II) complexes, preparation and reactivity, 4, 266 Bis-vinylic tellurides, preparation, 9, 605 Bis( -xylene)lead(II)bis(tetrachloroaluminate), preparation,... 

Bis-vinylic tellurides 68 can be prepared by reacting monosubstituted alkynes with a hydrotelluration system prepared from elemental tellurium and sodium borohydride in a mixture of ethanol/aqueous sodium hydroxide.133 The stereochemistry of the resulting vinylic tellurides is also Z (Equation (7)). 

The coupling reaction of tellurides with Grignard reagents promoted by Ni(ll) was described many years ago by LJemura.143 Recently, bis-vinylic tellurides were reacted with alkynes in the presence of catalytic amounts of Ni(dppe)Cl2 and Cul leading to enynes with retention of the (Z)-stereochemistry (Scheme 128).306... 

Kauffmann reported the first tellurium-lithium exchange reaction of a vinylic telluride with an organolithium compound.255 Phenyl vinyl telluride 168 was deprotonated by lithium dicyclohexylamide (LDCA) in THF, and the resulting vinyl anion 169 was reacted with chlorotrimethylsilane to give telluride 170. Vinylsilane telluroacetal 170 was then reacted with phenyllithium to give the corresponding vinyllithium, which was captured with chlorotrimethylsilane to give the bis-silylated ethane 171 (Scheme 96).255... 

Pd-catalyTxd coupling of vinylic tellurides with alkynes Pd-Te cationic intermediates were, for the first time, intercepted and transferred to the gas phase for structural characterization. Nucleophilic substitution reactions of methylated hydroxylamines with bis(2,4-dinitrophenyl) phosphate... 

Cyclopropanation of a,fi-unsaturated carbonyl compounds with dibromomalonates (typical procedure) To a mixture of diethyl dibromomalonate (0.95 g, 3 mmol) and methyl vinyl ketone (0.27 g, 3.1 mmol) is added dibutyl telluride (0.73 g, 3 mmol) under argon and with stirring. The exothermic reaction is completed within 1 h. The mixture is chromatographed on an AI2O3, column (70-230 mesh, elution with EtOAc), giving dibutyltellurium dibromide (1.01 g, 84%) and then l-acetyl-2,2-bis(ethoxycar-bonyl)cyclopropane, which is purified by Kiigelrohr distillation (0.59 g (86%) b.p. 88-90°C/0.08 torr). 

Hydrogen telluride, prepared from aluminum telluride and 2 molar hydrochloric acid, added to the double bond in vinyl cyanide and formed bis[2-cyanoethyl tellurium1. 

Phenylacetylene and sodium telluride combine to produce bis[(Z)-2-phenylethenyl] tellurium3, while phenylacetylene and sodium butanetellurolate3 or sodium benzenetel-lurolate4 yields organo (Z)-2-phenylethenyl telluriums. These vinyl telluriums are cleaved by butyl lithium in tetrahydrofuran at -78° to (Z)-2-phcnylcthenyl lithiums. 

Bis[2-cyanoethyl] tellurium was also reported to be obtained from vinyl cyanide and electrolytically generated hydrogen telluride. However, attempts to repeat this procedure failed. ... 

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