title: Stereoselectivity of 6-Exo Cyclization of α-Carbamoyl Radicals.
abstract: The stereoselectivity in the 6-exo cyclization of α-carbamoyl radicals was investigated experimentally and theoretically. The BEt3/O2-initiated iodine-atom-transfer radical cyclization reactions of substituted N-(but-3-en-1-yl)-N-(tert-butyl)-2-iodoalkanamides were carried out, which led to the predominant formations of 3,4-cis, 4,5-trans, or 4,6-trans substituted δ-lactams. Density functional calculations at the B3LYP/6-31G* level revealed that the 6-exo radical cyclization proceeds via boat-conformational transition states. Furthermore, a mechanistic insight into the stereoselectivity was provided and the calculation results were in excellent agreement with the experimental observations.
authors.affiliation: Key Laboratory of Organofluorine Chemistry and Collaborative Innovation Center of Chemistry for Life Sciences, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, P. R. China.
authors.forename: Liyan
authors.initials: L
authors.lastname: Song
authors.affiliation: Key Laboratory of Organofluorine Chemistry and Collaborative Innovation Center of Chemistry for Life Sciences, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, P. R. China.
authors.forename: Xinqiang
authors.initials: X
authors.lastname: Fang
authors.affiliation: Key Laboratory of Organofluorine Chemistry and Collaborative Innovation Center of Chemistry for Life Sciences, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, P. R. China.
authors.forename: Zijia
authors.initials: Z
authors.lastname: Wang
authors.affiliation: College of Chemistry, Tianjin Normal University , Tianjin 300387, P. R. China.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: School of Chemical Engineering, Ningbo University of Technology , No. 89 Cuibai Road, Ningbo 315016, P. R. China.
authors.forename: Chaozhong
authors.initials: C
authors.lastname: Li