Radical cyclizations have attracted considerable interest in recent years, both synthetically' and mechanistically.' Although radical cyclizations of alkyl radicals onto C=C and GO bonds' have been studied extensively, radical cyclizations to C=N bonds received relatively much less attention. Radical cyclizations of alkyl radicals onto C=N bonds of oxime ethers' and hydrazones' have been reported and their synthetic usefulness seems to be increasingly important." Recently, radical cyclization of alkyl radicals onto imines has been reported by Bowman.' The rate constants for the cyclization of alkyl radicals onto N,N-diphenylhydrazones8 and onto N-aziridinyl imines' were kinetically determined recently. The kmetic data showed that the cyclizations of alkyl radicals to C=N bonds of hydrazones were much faster than the cyclization of alkyl radicals to C=C and to C=O bonds, indicating that C=N bonds were much better radical acceptors than C=C and C=O bonds. However, neither unimolecular nor bimolecular rate constants for alkyl radical additions to imines have been reported. The only example for the rate constants of aryl radical additions to the imines was reported.'" Due to three different types of C=N bonds such as an imine, an oxime ether, and a hydrazone, we were initially interested in the dependence of the rate constants on the nature of C=N bonds. Specifically, we turned our attention to the following questions. (i) What are the effects of the electron density at iminyl carbons on radical cyclizations. (ii) Does the electron donating effect of the amino group in the hydrazone due to the resonance effect increase the cyclization rate 3 Since the resonance effect in the oxime ether and the hydrazone would increase the electron density at the iminyl carbon, (i) and (ii) seem to be closely related.