Three-component coupling sequence for the regiospecific synthesis of substituted pyridines
A de novo synthesis of substituted pyridines is described that proceeds through nucleophilic addition of a dithiane anion to an α,β- unsaturated carbonyl followed by metallacycle-mediated union of the resulting allylic alcohol with preformed trimethylsilane-imines (generated in situ by the low-temperature reaction of lithium hexamethyldisilazide with an aldehyde) and Ag(I)- or Hg(II)-mediated ring closure. The process is useful for the convergent assembly of di- through penta-substituted pyridines with complete regiochemical control.
Chen, Ming Z.,Micalizio, Glenn C.
p. 1352 - 1356
(2012/03/11)
Synthesis of dihydropyridines and pyridines from imines and alkynes via C-H activation
A convenient one-pot C-H alkenylation/electrocyclization/aromatization sequence has been developed for the synthesis of highly substituted pyridine derivatives from alkynes and α,β-unsaturated N-benzyl aldimines and ketimines that proceeds through dihydropyridine intermediates. A new class of ligands for C-H activation was developed, providing broader scope for the alkenylation step than could be achieved with previously reported ligands. Substantial information was obtained about the mechanism of the reaction. This included the isolation of a C-H activated complex and its structure determination by X-ray analysis; in addition, kinetic simulations using the Copasi software were employed to determine rate constants for this transformation, implicating facile C-H oxidative addition and slow reductive elimination steps.
Colby, Denise A.,Bergman, Robert G.,Ellman, Jonathan A.
p. 3645 - 3651
(2008/10/09)
(η3-Allyl)(η5-pentamethylcyclopentadienyl)cobalt - a Selective Catalyst for the Pyridine Synthesis
(η3-Allyl)(η5-pentamethylcyclopentadienyl)cobalt (1) cactalyses the synthesis of various pyridines from alkynes and nitriles under mild conditions.Only small amounts of benzenes are formed in this selective reaction. - Key Words: Cobalt complexes, (η3-allyl)(η5-pentamethylcyclopentadienyl)- / Pyridine synthesis / Catalytic activity / Chemoselectivity
Nehl, Hans
p. 2535 - 2538
(2007/10/02)
(Co)cyclodimerization of Alkynes by Aluminum Halides. Synthesis of Pyridines from Aluminum Halide ? Complexes of Cyclobutadienes and Nitriles
The Lewis acid promoted cyclodimerization of monoalkyl-substituted alkynes and cocyclodimerization of monoalkyl(aryl)- and dialkyl-substituted alkynes are described.It has been found that the corresponding aluminum halide ? complexes of the cyclobutadiene
Hogeveen, H.,Kingma, R. F.,Kok, D. M.
p. 989 - 997
(2007/10/02)
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