Telluroxide elimination by oxidation of alkyl aryl tellurides: remarkable effect of added triethylamine

Abstract

Treatment of various alkyl phenyl tellurides with 1–2 mol equiv. of m-chloroperbenzoic acid in diethyl ether in the presence of triethylamine at 25 °C for 2 h affords the corresponding alkenes highly selectively in fair to good yields. From stereochemical studies using erythro- and threophenyl 3-phenylbutan-2-yl tellurides as substrates it was revealed that, although Et₃N partly facilitates E2 elimination of the telluroxide, the main reaction course is the telluroxide synelimination (Ei elimination). Without the addition of Et₃N the elimination was quite slow in many cases, and in fact the compounds derived from the addition of m-chlorobenzoic acid to tetradecyl and cyclohexyl phenyl telluroxides were isolated, the pyrolysis (∼250 °C) of which afforded tetradec-1-ene and cyclohexene, respectively. A 2-pyridyltelluro moiety was revealed for the first time to be a better leaving group than a phenyltelluro moiety in telluroxide elimination.