Reactions involving electron transfer. VII. Use of intramolecular reactions as a test for anion radical intermediates

13C Kinetic Isotope Effects for the Addition of Lithium Dibutylcuprate to Cyclohexenone. Reductive Elimination Is Rate-Determining

“…The significant KIE at C a of the butyl group (1.011−1.016), though relatively small, suggests that C a is also undergoing a bonding change, i.e., the butyl group is being transferred in some fashion, in the rate-limiting step. Taken together, these results implicate reductive elimination as the rate-determining step. , …”

gem-Disubstituent Effect: Theoretical Basis and Synthetic Applications

“…Radical cyclizations are also extremely useful for the synthesis of five- and six-membered ring systems. One of the earlier reports on the cyclization of hex-5-enyl radicals ( 50 ) demonstrated that a gem -dimethyl group ( 50b ) enhances the rate of ring closure, which leads to the cyclopentane 52b as the major product (Scheme ) 20

21

22

24 Kinetic Data for 1,5-Ring Closure of Substituted Hexenyl Radicals in Benzene at 25 °Cradical k rel radical k rel 50a 1 54 21.86 50b 15.1 55 13.71 …”

Free-Radical Rearrangements

“…It has been firmly established that the 5-hexenyl radical, contrary to earlier indications (142), undergoes cyclization by intramolecular addition in a highly regiospecific fashion to afford mainly the cyclopentylcarbinyl radical (43,47,95,96,(143)(144)(145)(146)(147)(148)(149)(150)(151)(152)(153)(154)(155)(156)(157)(158).…”