17199-17-6Relevant articles and documents
Hemilabile Ligands in Organolithium Chemistry: Substituent Effects on Lithium Ion Chelation
Ramirez, Antonio,Lobkovsky, Emil,Collum, David B.
, p. 15376 - 15387 (2003)
The lithium diisopropylamide-mediated 1,2-elimination of 1-bromocyclooctene to provide cyclooctyne is investigated using approximately 50 potentially hemilabile polyethers and amino ethers. Rate laws for selected ligands reveal chelated monomer-based pathways. The dependence of the rates on ligand structure shows that anticipated rate accelerations based on the gem-dimethyl effect are nonexistent and that substituents generally retard the reaction. With the aid of semiempirical and DFT computational studies, the factors influencing chelation are discussed. It seems that severe buttressing within chelates of the substitutionally rich ligands precludes a net stabilization of the chelates relative to nonchelated (η 1-solvated) forms. One ligand-MeOCH2CH2NMe 2-appears to promote elimination uniquely by a higher-coordinate monomer-based pathway.
Stereospecific Palladium-Promoted Oxyamination of Alkenes
Baeckvall, Jan E.,Bjoerkman, Eva E.
, p. 2893 - 2898 (2007/10/02)
A method for direct oxyamination of olefins to vicinal amino alcohol derivatives is described. The reaction proceeds via an aminopalladation-oxidation sequence.Terminal olefins give good yields (60-80percent) whereas internal olefins give lower yields (20-60percent).The oxyamination reaction is stereospecific as shown by reaction of (Z)- and (E)-2-butene and (E)-1-deuterio-1-decene and proceeds by overall cis stereochemistry.The stereochemical outcome is a result of a trans aminopalladation followed by an oxidative cleavage of the palladium carbon bond with inversion of configuration at carbon.Oxidation of the organopalladium ? complex to give an oxidized palladium intermediate, which could be a Pd(IV) intermediate, followed by SN2-type nucleophilic displacement of palladium is the most likely mechanism for the oxidative cleavage reaction.
