Aryl telluroesters

Although the photochemistry of aryl selenoesters and aryl telluroesters is not fully developed, there are some photoreactions of these compounds that resemble a photo-Fries process. Se-/ ara-tolyl selenobenzoate (212) gives, upon irradiation, selenocresol (214), benzaldehyde, and the benzophenone 213 (Scheme 56), which is clearly a photo-Fries product [157,158], Starting from Se-phenyl 2-chlorosele-... 

Telluroesters have also been employed as starting materials in teUuro vinylation reactions. Thus, by treatment of telluroesters with aryl propiolates in the presence of KjCOj, (Z)-/(-acyltellurocinnamates are formed in high yields. This procedure involves the addition of potassium aryltellurolate anions derived from the telluroesters. " ... 

Typical procedure for rearrangement with aryl tellurium group transfer (formation of 3-[(aryltelluro)methyl]chromanones)f In a 5 mL flask fitted with a reflux condenser the telluroester (0.1 mmol) was photolysed under argon in benzene (3 mL) with a 250 W GE sunlamp from a distance of 15 cm. Either no cooling bath was used and the heat from the lamp caused the solution to reflux or the reaction was maintained at 8°C by means of a circulating cold water bath. After completion (TEC control) the solvent was removed in vacuo and the residue analysed by NMR spectroscopy. 

Apart from aryl esters and amides of carboxylic acids, aryl carbonates, and carbamates, other types of organic compound have been reported to undergo PFR. They include oxalates, formiates, sulfonates, sulfonamides, thioesters, selenoesters, and telluroesters. 

Another access to alkyl and aryl acyllithiums is based on a tellurium-lithium exchange58. Thus, telluroesters 44 reacted with n-BuLi at —105 or —78 °C in the presence of pinacolone or chlorotrimethylsilane to afford products 45 or 46, respectively (Scheme 11). However, selenoesters and acylstannanes did not give the corresponding adducts under similar reaction conditions. 

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