discussed. A correlation by which the rate constant for the C-O bond cleavage of TEMPO-derived alkoxyamines can be predicted from the C-H BDEs of the corresponding alkanes is presented. Solvent effects as well as the effect of camphorsulfonic acid on the rate of the C-O bond homolysis are discussed. Finally, EPR and kinetic evidence show that alkoxyamines derived from nitroxides which are capable of intramolecular
Tin-Free Radical Alkoxyamine Addition and Isomerization Reactions by Using the Persistent Radical Effect: Variation of the Alkoxyamine Structure
作者:Kian Molawi、Tobias Schulte、Kai Oliver Siegenthaler、Christian Wetter、Armido Studer
DOI:10.1002/chem.200400936
日期:2005.4.8
Various C-centered radicals can efficiently be generated through thermal C-O-bond homolysis of alkoxyamines. This method is used to perform environmentally benign radical cyclization and intermolecular addition reactions. These alkoxyamine isomerizations and intermolecular carboaminoxylations are mediated by the persistent radicaleffect (PRE). In the paper, the effect of the variation of the alkoxyamine
Generation and intramolecular cyclization of α-phenylsulfenyl and α-alkylsulfenyl radicals
作者:Yeun-Min Tsai、Fu-Chang Chang、Jimin Huang、Chi-Lung Shiu、Chai-Lin Kao、Jyh-Shiunn Liu
DOI:10.1016/s0040-4020(97)00156-7
日期:1997.3
alpha-Phenylsulfenyl radicals are generated by the reaction of diphenyl dithioacetals or phenyl alpha-chlorosulfides with tributyltin hydride. Alkyl phenyl dithioacetals react selectively with tributyltin hydride to give alpha-alkylsulfenyl radicals. 5-Exo-type of intramolecular cyclizations of these radicals are studied. The cyclization is most successful when the olefin is terminally substituted with an ester group. The cis/trans ratio of the cyclized product varies according to the reaction rates. With a faster cyclization, cis-isomer is the major product. A slower cyclization gives more trans-product. (C) 1997 Elsevier Science Ltd.
Generation and intramolecular cyclization of α-sulfinyl and α-sulfonyl radicals
作者:Bor-Wen Ke、Chao-Hsiung Lin、Yeun-Min Tsai
DOI:10.1016/s0040-4020(97)00472-9
日期:1997.6
alpha-Phenylsulfinyl and alpha-Phenylsulfonyl radicals are generated by the reactions of alpha-chlorosulfoxides and alpha-chlorosulfones with tributyltin hydride, respectively. High reaction concentration (0.2 M) is required to ensure efficient generations of these radicals. The 5-exo-type intramolecular cyclizations of these radicals are studied. The cyclization is most successful when the olefin is terminally substituted with an ester group. The sulfinyl group only induces mild diastereoselectivity on the cyclization. (C) 1997 Elsevier Science Ltd.
Tin-Free Radical Cyclization Reactions Using the Persistent Radical Effect