TELLUROXIDE ELIMINATION BY OXIDATION OF ALKYL ARYL TELLURIDES - REMARKABLE EFFECT OF ADDED TRIETHYLAMINE

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-degrees-C for 2 h affords the corresponding alkenes highly selectively in fair to good yields. From stereochemical studies using erythro- and threo-phenyl 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 syn-elimination (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 (approximately 250-degrees-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.