2- Naphthyltellurium trichloride

Naphthyltellurium trichloride (typical procedure) TeCl4 (7.5 g, 27.8 mmol) is added to molten naphthalene (11.0 g, 86 mmol) kept at 110°C under N2. After 12 h at this temperature the greenish solid obtained is pulverized in a mortar and washed thoroughly with hot toluene (15.4 g (54%)). The product is recrystallized from benzene (m.p. 200-202°C). 

Chloroalkyl-2-naphthyltellurium dichloride (general procedure). 2-Naphthyltellurium trichloride (2.98 g, 0.83 mmol) is heated under reflux with the olefin (1.2 mmol) in dry, ethanol-free CHCI3 (15 mL) until the trichloride has dissolved (0.5-1 h). Filtration from a small amount of elemental Te and evaporation gives an oil or a semi-solid that is recrystallized from a large amount of petroleum ether at 40-60°C. The reactions with propene and 2-butenes are performed in a sealed tube at 80°C. The yields are in the range 70-95%. 

It has been rationalized that these reactions proceed via a cyclic telluronium ion intermediate which undergoes a nucleophilic attack by the chloride ion giving the products with trans configuration. The addition of 2-naphthyltellurium trichloride to a variety of acyclic and cyclic alkenes is completely anti or trans stereoselective, but tellurium tetrachloride usually gives mixtures arising from syn (cis) and anti (trans) addition representative results are presented in Tables 15 and 16. 

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