title: Reactions of iron carbenes with α,β-unsaturated esters by using an Umpolung approach: mechanism and applications.
abstract: An Umpolung approach, in which a phosphorus ylide moiety was introduced to increase the electron density of the double bond, was developed to activate electron-deficient alkenes for reaction with electrophilic iron carbenes. In tandem with the Wittig reaction, the reactions of α,β-unsaturated esters with in situ generated Fe-carbene complexes delivered formal C-H insertion products through cyclopropanation/ring-opening reactions. DFT calculations and cross-experiments indicate that, in this process, the ring opening of the cyclopropylmethyl ylide intermediate is rapid and reversible and the subsequent proton transfer is the rate-determining step. Further studies revealed that, based on the choice of the ylide and ester groups, as well as the base, the reaction could be steered towards either the ring-opening pathway or to the production of vinyl cyclopropanes.
authors.affiliation: State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, PR China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Lin
authors.initials: L
authors.lastname: Ling
authors.forename: Sai-Hu
authors.initials: SH
authors.lastname: Liao
authors.forename: Jian-Bo
authors.initials: JB
authors.lastname: Zhu
authors.forename: Sunewang R
authors.initials: SR
authors.lastname: Wang
authors.forename: Yu-Xue
authors.initials: YX
authors.lastname: Li
authors.forename: Yong
authors.initials: Y
authors.lastname: Tang