Reactions of Benzenetellurol as a Reducing Agent

Abstract

The reduction of benzenetellurol has been studied in detail. Benzenetellurol is generated in situ by methanolysis of phenyltellurotrimethylsilane
. Since the conversion is rapid and the sole by-product, methyl trimethylsilyl ether, does not interfere with the reaction of benzenetellurol, this provides a method of choice for examining the reactivity of benzenetellurol itself under neutral conditions.
A variety of nitro com pounds were smoothly reduced with benzenetellurol to the corresponding amines at room temperature in benzene (Table 1). Aldehydes and phenyl ketones were similarly converted into primary and secondary alcohols, respectively (Table 4). Moreover, olefinic or acetylenic compounds conjugating with a phenyl or carbonyl group were hydrogenated by benzenetellurol (Table 5). Effects of sunlight (Fig.1), reaction temperature, and additives (Table 8) on reduction of carbonyl and olefinic compounds suggested that these reactions proceeded via a mechanism involving initial electron transfer from benzenetellurol to substrate (Scheme 3).
On the other hand, secondary alkyl tellu rides were converted into alkanes via thermal or photoinduced radical process (Table 6, Scheme 4). Primary alkyl tellurides resisted the reduction. Acetals were not reduced with benzenetellurol under normal conditions but to the corresponding ethers in high yields by using ZnI₂ as a catalyst (Table 7).