A Carbon Centered Radical Unreactive Towards Oxygen: Unusual Radical Stabilization by a Lactone Ring
J.C. Scaiano, A. Martin, G.P.A. Yap and K.U. Ingold, “A Carbon Centered Radical Unreactive Towards Oxygen: Unusual Radical Stabilization by a Lactone Ring”, Org. Lett., 2 (7), 899-901 (2000).
A lactone ring confers unusual stability to a diphenylmethyl-like radical that is virtually unreactive toward oxygen. Thus, the radical derived from HP-136 is about 10 000 times less reactive than typical carbon-centered radicals. A reversible reaction with oxygen is proposed by analogy with triphenylmethyl; however, the association constant is about 1000 times smaller for HP-136 than for triphenylmethyl. While the lactone ring greatly influences the reactivity, the spectroscopy of the HP-136-derived radical is in line with that expected for a substituted diphenylmethyl radical.