The Cross-Reaction Between 1-Methoxycarbonyl-1-Methylethyl and 1-Butoxycarbonyl-1-Methylethyl: Simultaneous Generation of Unlike Radicals From an Unsymmetrical Azo Precursor

Abstract

The title radicals (1a) and (1b) were generated simultaneously by thermolysis of the unsymmetrical diazene, butyl methyl azoisobutyrate (2d). In the presence of the radical scavenger 2,2,6,6- tetramethylpiperidin-1-yloxyl (4) the products of the geminate cross-reaction show that 45% of radical pairs react by combination and 55% by disproportionation. The disproportionation reaction shows a slight preference for hydrogen transfer from the butyl ester (lb) to the methyl ester (la) radical. In the absence of scavenger (4), the encounter reactions of the two radicals show a slight preference for the cross-reaction over the two self-reactions which is most likely largely due to the imbalance in radical concentrations caused by the greater reactivity toward addition to olefins of the methyl ester radical.