Rate Constants for 5- and 6-Exo Secondary Alkyl Radical Cyclizations onto N,N-Diphenylhydrazones
作者:Claudio F. Sturino、Alex G. Fallis
DOI:10.1021/jo00101a007
日期:1994.11
Competitive ''radical clock''-type cyclizations of hydrazones and alkenes established that the rate constants for 5-exo cyclizations onto N,N-diphenylhydrazones are 1.1 x 10(8) s(-1) and 4.6 x 10(7) s(-1) at 80 degrees C to the cis- and trans-cyclopentylhydrazines, respectively (about 200 times faster than the corresponding cyclization rate for 5-exo alkenes). The 6-exo hydrazone rate constant is 9.4 x 10(5) s(-1) at 80 degrees C for both cis and trans isomers with activation barriers of 5.6 and 6.2 kcal/mol, respectively.