Contra-thermodynamic Olefin Isomerization by Chain-Walking Hydroboration and Dehydroboration
作者:Steven Hanna、Brandon Bloomer、Nicodemo R. Ciccia、Trevor W. Butcher、Richard J. Conk、John F. Hartwig
DOI:10.1021/acs.orglett.1c03124
日期:2022.2.4
chain-walking hydroboration to create a one-pot, contra-thermodynamic, short- or long-range isomerization of internal olefins to terminal olefins. This dehydroboration occurs by a sequence comprising activation with a nucleophile, iodination, and base-promoted elimination. The isomerization proceeds at room temperature without the need for a fluoride base, and the substrate scope of this isomerization is expanded
The synthesis methods, physicochemical and structural characteristics, and catalytic reactivity of new macrocyclic proton chelators, N,N ',N ''-tris(p-tolyl)azacalix[3](2,6)(4-pyrrolidinopyridine) and N,N ',N ''-tris(p-tolyl)azacalix[3](2,6)(4-piperidinopyridine), are studied. The introduction of pyrrolidino and piperidino groups into the pyridine unit enables the enhancement of the synergistic proton affinity of the cavity of the macrotricycle giving a high basicity (pK(BH+) = 28.1 and 27.1 in CD3CN), resulting in a catalytic activity for the Michael addition of nitromethane with alpha,beta-unsaturated carbonyl compounds.
Molecular Design of Organic Superbases, Azacalix[3](2,6)pyridines: Catalysts for 1,2- and 1,4-Additions
The molecular design, characteristics, and catalytic activity of macrocyclic amino compounds, azacalix[3](2,6)pyridine derivatives, were studied. The introduction of an electron-donating group on the pyridine moiety and bridging amino phenyl group enabled the enhancement of the basicity of azacalix[3](2,6)pyridine up to pK(BH+) = 29.5 in CD3CN. These derivatives were shown to be efficient catalysts for 1,4-addition reactions of nitroalkanes or primary alcohols to alpha,beta-unsaturated carbonyl compounds and 1,2-addition reactions of nitroalkanes to aromatic aldehydes.
Template-directed synthesis of macrocyclic aminopyridines: azacalix[n](2,6)pyridines (n=3, 4)
Template-induced synthetic routes for azacalix[n](2,6)pyridines (n = 3, 4) have been elaborated. The proton and nickel ion served as the efficient template for the cyclization reactions, and the presence of the templates preferentially afforded the cyclic trimers and tetramers in moderate to good yields, respectively. The compatibility of the cyclic tetramer with nickel ion was also confirmed by X-ray crystallography. (C) 2014 Elsevier Ltd. All rights reserved.