title: Silver-Catalyzed Amidiniumation of Alkynes: Isolation of a Silver Intermediate, Synthesis of Enamine Amido Carbene Precursors, and an Unprecedented Umpolung of Propiolamide.
abstract: A silver-catalyzed amidiniumation of N-propiolic formamidines for the synthesis of novel enamine amido carbene precursors is reported. Isolation of a first silver intermediate in silver-catalyzed amidiniumation of alkynes and other organogold intermediates supports our proposed mechanisms. Several control experiments reveal the unexpected effects of both HOTf and substrate substituents on the choice of either a π or σ,π silver activation mode and the cyclization fashion. Bis(hydroxyimidazol)ium salts were obtained through an unprecedented umpolung of propiolamides. The byproduct Ag2O as either an oxidant or silver source promotes the syntheses of N-heterocyclic carbene (NHC) precursors or Ag/NHC complexes.
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237 (China).
authors.forename: Shichang
authors.initials: S
authors.lastname: Lv
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237 (China).
authors.forename: Jiwei
authors.initials: J
authors.lastname: Wang
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237 (China).
authors.forename: Caiyun
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237 (China).
authors.forename: Sheng
authors.initials: S
authors.lastname: Xu
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237 (China).|State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032 (China).
authors.forename: Min
authors.initials: M
authors.lastname: Shi
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237 (China). zhangj@ecust.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
keywords: alkynes; carbenes; cyclizations; reaction mechanisms; silver