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Yuefei Hu – 1st expert on this subject based on the ideXlab platform

  • enantiopure 2 6 disubstituted piperidines bearing one alkene or Alkyne containing substituent preparation and application to total syntheses of indolizidine alkaloids
    ChemInform, 2010
    Co-Authors: Deyong Su, Guolin Cheng, Jimin Xu, Xinyan Wang, Yuefei Hu

    Abstract:

    Starting with the known precursor (I), a library of 18 optically active 2,6-disubstituted piperidines such as (VI) carrying one alkene or Alkyne moiety is prepared.

  • enantiopure 2 6 disubstituted piperidines bearing one alkene or Alkyne containing substituent preparation and application to total syntheses of indolizidine alkaloids
    Organic and Biomolecular Chemistry, 2010
    Co-Authors: Deyong Su, Guolin Cheng, Jimin Xu, Xinyan Wang, Yuefei Hu

    Abstract:

    A general and efficient procedure for the preparation of 2,6-disubstituted piperidines bearing one alkene- or Alkyne-containing substituent was developed by using non-racemic Betti base as a chiral auxiliary. Many chiral benzylamines are excellent auxiliaries, but they were rarely used for this purpose because of the inefficient removal of the N-benzyl auxiliary residue under non-hydrogenative conditions. We found that N,N-disubstituted Betti base derivative has a typical Mannich structure of o-naphthol. When it carried out a base-catalyzed formation of o-quinone methide, an efficient non-hydrogenative N-debenzylation was achieved, and the alkene and Alkyne groups survived. To demonstrate the efficiency of the method and the versatility of the products, asymmetric total syntheses of indolizidine-alkaloids (−)-167B, (−)-195H, (−)-209D and (−)-223AB were accomplished.

Antonio M Echavarren – 2nd expert on this subject based on the ideXlab platform

  • gold i catalyzed activation of Alkynes for the construction of molecular complexity
    Chemical Reviews, 2015
    Co-Authors: Ruth Dorel, Antonio M Echavarren

    Abstract:

    1.1. General Reactivity of Alkyne-Gold(I) Complexes
    For centuries, gold had been considered a precious, purely decorative inert metal. It was not until 1986 that Ito and Hayashi described the first application of gold(I) in homogeneous catalysis.1 More than one decade later, the first examples of gold(I) activation of Alkynes were reported by Teles2 and Tanaka,3 revealing the potential of gold(I) in organic synthesis. Now, gold(I) complexes are the most effective catalysts for the electrophilic activation of Alkynes under homogeneous conditions, and a broad range of versatile synthetic tools have been developed for the construction of carbon–carbon or carbon–heteroatom bonds.

    Gold(I) complexes selectively activate π-bonds of Alkynes in complex molecular settings,4−10 which has been attributed to relativistic effects.11−13 In general, no other electrophilic late transition metal shows the breadth of synthetic applications of homogeneous gold(I) catalysts, although in occasions less Lewis acidic Pt(II) or Ag(I) complexes can be used as an alternative,9,10,14,15 particularly in the context of the activation of alkenes.16,17 Highly electrophilic Ga(III)18−22 and In(III)23,24 salts can also be used as catalysts, although often higher catalyst loadings are required.

    In general, the nucleophilic Markovnikov attack to η2-[AuL]+-activated Alkynes 1 forms trans-alkenyl-gold complexes 2 as intermediates (Scheme 1).4,5a,9,10,12,25−29 This activation mode also occurs in gold-catalyzed cycloisomerizations of 1,n-enynes and in hydroarylation reactions, in which the alkene or the arene act as the nucleophile.

    Scheme 1

    Anti-Nucleophilic Attack to η2-[AuL]+-Activated Alkynes

  • gold catalyzed synthesis of tetrazoles from Alkynes by c c bond cleavage
    Angewandte Chemie, 2013
    Co-Authors: Morgane Gaydou, Antonio M Echavarren

    Abstract:

    Cycloadditions of azides with Alkynes to form triazoles under thermal conditions (Huisgen cycloaddition)[1] or in the presence of copper [click reaction, copper-catalyzed azide–Alkyne cycloaddition (CuAAC)][2,3] are reactions of fundamental importance in organic chemistry. Triazoles can also be obtained by means of ruthenium,[4] silver,[5] and iridium[6] catalysis, as well as by a zinc-mediated process.[7] In sharp contrast, very different reactivity has been observed in the reaction of terminal Alkynes with TMSN3 in the presence of group 11 metal salts and complexes.[8] Thus, the group of Jiao recently made the remarkable observation that Alkynes (1; R=alkyl, aryl, alkenyl) react with TMSN3 in the presence of Ag2CO3 as catalyst to form nitriles (2; Scheme 1).[9] The same group has reported the cleavage of the aryl–Alkyne C(sp2)=C(sp) bond of Alkynes (1) using [Au(PPh3)Cl] and AgCO3 in the presence of H2O and trifluoroacetic acid (TFA) to form carboxamides.[10]

  • PtII catalyzed intramolecular reaction of furans with Alkynes
    Angewandte Chemie – International Edition, 2001
    Co-Authors: Belén Martín-matute, Diego J Cardenas, Antonio M Echavarren

    Abstract:

    The intramol. reactions of furans with Alkynes catalyzed by PtCl2 was studied . Using DFT, several pathways can be predicted in principle, starting with the coordination of the Alkyne to the metal center. The mechanism involved first, the Diels-Alder reaction between the furan and the coordinated Alkyne could give intermediate, second the formation of a cyclopropyl Pt carbene by the reaction of the Alkyne with the C2-C3 double bond of furan could occur. The third mechanism involved Friedel-Crafts-type reaction of the electron-deficient Alkyne at C2 of the furan. Results showed that the intramol. reaction of furans with Alkynes catalyzed by PtCl2 was mechanistically related to the enzymes in the polar solvents and was initiated by the nucleophilic attack of the furan on an η 2-Alkyne platinum complex to form a cyclopropyl platinum carbene. [on SciFinder(R)]

Deyong Su – 3rd expert on this subject based on the ideXlab platform

  • enantiopure 2 6 disubstituted piperidines bearing one alkene or Alkyne containing substituent preparation and application to total syntheses of indolizidine alkaloids
    ChemInform, 2010
    Co-Authors: Deyong Su, Guolin Cheng, Jimin Xu, Xinyan Wang, Yuefei Hu

    Abstract:

    Starting with the known precursor (I), a library of 18 optically active 2,6-disubstituted piperidines such as (VI) carrying one alkene or Alkyne moiety is prepared.

  • enantiopure 2 6 disubstituted piperidines bearing one alkene or Alkyne containing substituent preparation and application to total syntheses of indolizidine alkaloids
    Organic and Biomolecular Chemistry, 2010
    Co-Authors: Deyong Su, Guolin Cheng, Jimin Xu, Xinyan Wang, Yuefei Hu

    Abstract:

    A general and efficient procedure for the preparation of 2,6-disubstituted piperidines bearing one alkene- or Alkyne-containing substituent was developed by using non-racemic Betti base as a chiral auxiliary. Many chiral benzylamines are excellent auxiliaries, but they were rarely used for this purpose because of the inefficient removal of the N-benzyl auxiliary residue under non-hydrogenative conditions. We found that N,N-disubstituted Betti base derivative has a typical Mannich structure of o-naphthol. When it carried out a base-catalyzed formation of o-quinone methide, an efficient non-hydrogenative N-debenzylation was achieved, and the alkene and Alkyne groups survived. To demonstrate the efficiency of the method and the versatility of the products, asymmetric total syntheses of indolizidine-alkaloids (−)-167B, (−)-195H, (−)-209D and (−)-223AB were accomplished.