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Racemization of chiral imidazolines with base has been studied for the first time following an unexpected finding in the synthesis of chiral imidazoline ligands. Amine bases do not cause racemization. Strong inorganic bases can induce racemization, yet this occurs only when the nitrogen is unsubstituted, in agreement with a symmetry-allowed thermal… (More)
Solid state (31)P NMR spectroscopy was used to examine, monitor and quantify the compound integrity of the chemical reagent dichlorotriphenylphosphorane. Comparison was also made with solution (31)P NMR spectra which showed that this highly reactive species could be observed in dry benzene prior to conversion to the hydrolyzed product. This is the first… (More)
Vinylallenes or cross-conjugated trienes are obtained selectively in the title reaction. Two possible mechanisms are suggested to rationalize the formation of the different types of products. Control experiments indicate that p-benzoquinone (BQ) plays an important role as a ligand in addition to its role as an oxidant. E=CO(2)Me.
An enantioselective oxidative carbocyclization-borylation of enallenes that is catalyzed by palladium(II) and a Brønsted acid was developed. Biphenol-type chiral phosphoric acids were superior co-catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess.
Highly selective protocols for the carbocyclization/arylation of allenynes using arylboronic acids are reported. Arylated vinylallenes are obtained with the use of BF3⋅Et2O as an additive, whereas addition of water leads to arylated trienes. These conditions provide the respective products with excellent selectivities (generally >97:3) for a range of… (More)
The first report of monitoring the kinetics of racemization in solution by online vibrational circular dichroism (VCD), chemometrics, and density functional theory (DFT) calculations is presented. The activation energy for the racemization of an imidazoline based on the experimental VCD was determined, and the detailed mechanism of the process utilizing DFT… (More)