Kinetic and theoretical study of 4-exo ring closures of carbamoyl radicals onto C=C and C=N bonds.
Carbamoyl radicals were generated from oxime oxalate amides, and the kinetics of their 4-exo cyclizations onto C=C and C=NO bonds, leading to beta-lactam-containing species, were studied by EPR spectroscopy. DFT computations with model carbamoyl radicals predicted 4-exo ring closures onto C=NO bonds to be facile, especially when tert-butyl substituents were present. The reverse ring-opening reactions were predicted to have much higher activation energies. Experimental evidence also favored slow reverse ring opening.
Dilabio
Gino A
GA
School of Chemistry, University of St. Andrews, St. Andrews, Fife, UK KY16 9ST.
Scanlan
Eoin M
EM
Walton
John C
JC