N,3,4-Tri substituted pyrrolidines by electron transfer-induced oxidative cyclizations of N-allylic beta-amino ester enolates

作者：Jahn Ullrich^*; Kafka Frantisek; Pohl Radek; Jones Peter G

来源：Tetrahedron, 2009, 65(52): 10917-10929.

DOI：10.1016/j.tet.2009.10.034

Oxidative radical cyclizations starting from easily accessible N-allylic beta-alanine esters are reported. Deprotonation generates the corresponding enolates, which are transformed efficiently into alpha-ester radicals by single electron transfer mediated by ferrocenium hexafluorophosphate. The stereochemistry of the radical 5-exo cyclization can be switched by the configuration of the enolate precursor. First examples of asymmetric oxidative radical cyclizations using N-(1-phenylethyl)-substituted beta-amino esters are reported. Only two of the four possible diastereomers are formed from the (E)-enolate with high cis-selectivity. From (Z)-enolates, an additional diastereomer is formed, which is likely to be formed only under chelation control.

• 出版日期2009-12-26