Thermolysis of Geminal Bisazoalkanes. Stabilization of a Carbon-Centered Radical by the Azo Substituent

Article abstract of DOI:10.1021/jo00100a028

Two geminal bisazoalkanes (1 and 2) have been employed to generate a radical center next to the azo group.The 8.0 kcal/mol lower ΔG(excit.) for thermolysis of 1 and 2 relative to model compounds 6 and 7 is dissected into a 1 kcal/mol contribution from ground state elevation of 1 and 2 and at least 2.6 kcal/mol from phenyl stabilization of radical 3.Any extra stabilization of the aliphatic 2,3-diazaallyl radical (4) relative to α,α-dimethylallyl amounts to no more than 4.4 kcal/mol.Finally, γ-phenyl conjugation of the α,α-dimethylallyl radical stabilizes it by 4.5 kcal/mol.