title: Tuning the reactivity of isocyano group: synthesis of imidazoles and imidazoliums from propargylamines and isonitriles in the presence of multiple catalysts.
abstract: The reaction of propargyl amines with tert-butylisonitrile in the presence of a catalytic amount of both Yb(OTf)3 and AgOTf afforded imidazoles, whereas the same reaction with primary and secondary alkylisonitriles, as well as arylisonitriles, in the presence of three metal salts [Yb(OTf)3/AgOTf/KOTf] resulted in the 1,3,4,5-tetrasubstituted imidazoliums in excellent yields. Both chiral amines and chiral isonitriles can be used to provide corresponding chiral heterocycles without racemization. In this multiple catalytic system, Yb(OTf)3 catalyzed the insertion of isonitriles to the N-H bond of amines, AgOTf catalyzed the 5-exo-dig cyclization of the resulting amidine nitrogen to the tethered triple bond, and KOTf promoted the salt metathesis, thus providing at the same time the counterion to the imidazolium. Against common knowledge, the isocyano group acted in these reactions as a polarized triple bond instead of conventional carbene-like function.
authors.affiliation: Laboratory of Synthesis and Natural Products, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LSPN, BCH 5304, 1015 Lausanne (Switzerland) http://lspn.epfl.ch.
authors.forename: Shuo
authors.initials: S
authors.lastname: Tong
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.forename: Mei-Xiang
authors.initials: MX
authors.lastname: Wang
authors.forename: Jieping
authors.initials: J
authors.lastname: Zhu
mesh_terms: D002384:Catalysis; D007093:Imidazoles / Q000138:chemical synthesis / Q000737:chemistry*; D007536:Isomerism; D008698:Mesylates / Q000737:chemistry; D009570:Nitriles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry; D010293:Pargyline / Q000031:analogs & derivatives* / Q000737:chemistry; D011437:Propylamines / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D008698:Mesylates; D009570:Nitriles; D009942:Organometallic Compounds; D011437:Propylamines; C009054:propargylamine; C518808:ytterbium(III) triflate; D010293:Pargyline; C012077:trifluoromethanesulfonic acid
keywords: heterocycles; homogeneous catalysis; multicomponent reactions; silver; synthetic methods