Telluroesters as source of acyl radicals

Telluroesters (acyl tellurides) have been recognized as excellent sources of acyl radicals upon photolysis with a 250 W tungsten lamp, or thermal process (benzene at reflux) in the 

The formed acyl radicals are reactive towards efficient radical trapping reagents such as 2,2,6,6-tetramethylpiperidine-l-oxyl radical (TEMPO), diphenyl diselenide and diphenyl disulphide, and A-f-butyl-a-phenylnitrone giving the respective adducts.  

Photolytic reaction of telluroesters typical procedure for photolysis in the presence of TEMPO f Photolysis of the telluroester (Ar = T-FCgH ) (34 mg, 0.1 mmol) and TEMPO 

S-phenyl thiobenzoate typical procedure in the presence of diphenyl disulphide. Photolysis of the telluroester (Ar = 4-FCgH4) in the presence of 6 equiv of diphenyl disulphide according to the standard for the formation of selenoesters gave 71% of the thiobenzoate after chromatography on silica gel (eluent hexane/ ethyl acetate, 9 1). The product had a melting point and spectral characteristics in accordance with those described in the literature. 

Further evidence for the generation of acyl radicals is the formation of benzaldehyde on photolysis of benzoyl-1-naphthyl telluride in the presence of thiophenol. 

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