Allyl telluroxides

The reaction intermediate is an unstable and not isolated phenyl allyl telluroxide. Arylamines behave similarly, bnt require longer reaction times. 

Allylstlanes — allylaminesThe conversion is effected with 1 catalyzed by BF, etherate and is believed to involve an intermediate allyl telluroxide (a), which... 

This result is consistent with an equilibrium between an initially formed a-substituled allyl telluroxide (resulting from the well-known regio-controlled electrophilic attack at the y-carbon) and the y-isomer (which is really the main product, as detected by NMR). In the subsequent reaction with amines, the more nucleophilic alkylamines attack the central carbon atom, giving rearranged products, whereas the less nucleophilic arylamines attack the terminal carbon, giving the thermodynamic y-product. 

Since the starting tellurides are easily prepared (see Section 3.1.3.2) from the corresponding alkyl bromides and tellurolate ions, and -hydroxyalkyl tellurides by the opening of epoxides with the same reagents, the combined procedures furnish a method for the dehydrobromination of alkyl bromides and for the conversion of epoxides into allylic alcohols. Moreover, combining the telluroxide elimination with the methoxytelluration of olefins (see Sections 3.9.3.2 and 4.4.8.3), allylic and vinylic ethers are easily prepared. 

Method d. The dibromide is converted into the stable telluroxide hydrate and then pyrol-ysed to the allylic and vinylic methyl ether as described previously. 

The telluroxide elimination in allylic tellnrides proceedes via a [2,3]-sigmatropic rearrangement affording allylic alcohols after hydrolysis. ... 

Benzenetellurinyl trifluoroacetate and allyltrimethylsilanes reacted in 1,2-dichloroethane at 20° in the presence of boron trifluoride diethyl etherate to produce allyl phenyl telluroxides. The unstable telluroxides were not isolated but detected in solution by NMR spectroscopy. They were reduced to allyl phenyl tellurium derivatives with hydrazine hydrate. 

When solutions of the allyl phenyl telluroxides were treated at 65° with anilines, piperidine, primary aliphatic amines, or secondary aliphatic amines, allylamines were obtained in yields ranging from 15 to 95 %3. 

As in the selenium case (Scheme 17) the oxidation of alkyl phenyl telluride with excess MCPBA in the presence of alcohols results in a facile substitution of a PhTe moiety by an alkoxy group. The reaction is assumed to proceed via a similar tellurone-MCPBA adduct intermediate. Oxidation of cycloalkyl telluride (61) was accompanied by ring contraction to produce an acetal (62), < while the bromination-hydrolysis method affords the allylic ether by telluroxide elimination (Scheme 22). ... 

Allyl phenyl telluriums, prepared from allyl halides and benzenetellurolate, experience oxidative cleavage of the allyl group when treated with hydrogen peroxide, tcrr.-butyl hydroperoxide, sodium periodate, oxygen, or air The allyl group is converted to unsaturated alcohols, aldehydes, and ketones. Before elimination from the molecule the phenyltelluro group is probably oxidized to a telluroxide or a tellurinic ester ... 

Nucleophilic oxirane ring opening with sodium phenyltellurate (Na+ C6H5Te ), followed by telluroxide elimination with base, has been employed as a two-step protocol for isomerizations to allyl alcohols <82TL1177, 83JOM(250)203>. 

---