The reactions of t-butoxyl with unsaturated hydrocarbons: Structure and reactivity of allylic radicals

Abstract

A radical trapping technique employing 1,1,3,3-tetramethylisoindolin-2-yloxy(1) as scavenger has been used to study the reactions of t-butoxy radicals with propene, 2-methylpropene, but-1-ene, (E)- and (Z)-but-2-ene, 3-methylbut-1-ene, buta-1,3-diene and 2-methylbuta-1,3-diene. Relative rates of double bond addition and of allylic hydrogen abstraction have been measured and are discussed, as are the relative stabilities of the products formed. The allylic radicals generated in these systems react with (1) mainly by coupling at the more substituted terminus of the radical π system. Substituent effects on this regioselectivity may be explained in terms of the electrophilicity of (1).