UNEXPECTED PRODUCTS FROM THE REACTION OF TERT-BUTOXYL RADICALS WITH ACETYLENES IN THE PRESENCE OF AN AMINOXYL RADICAL SCAVENGER

The radical trapping technique employing 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl (1) as a scavenger has been used to study the reaction of tert-butoxyl radicals with phenylacetylene, methyl acetylenecarboxylate and dimethyl acetylenedicarboxylate. With phenylacetylene, an aromatic ketone (5) was formed in which both the tert-butoxy group and the radical trap were bound to the same carbon, whereas the acetylenecarboxylates gave vinylamine and vinyloxyamine products. The mechanism of formation of these unexpected products is discussed. Acetylene and diphenylacetylene did not appear to react with tert-butoxyl radicals.