The ability of chiral diamine silver complexes to bind chiral and prochiral alkenes has
been analyzed in detail. The stereoselectivity in binding of alkenes to a chiral ethanediamine
silver complex has been investigated by NMR. The low-energy conformations of several small
model complexes have been explored by DFT methods. By successive substitution of the
computational model complexes, it has been possible to elucidate the role of each amine
substituent in achieving successful discrimination of alkenes. The conformational space has
been fully explored using small model systems, allowing an unbiased calculation of
stereoselectivities that match well the experimental results. For a chiral allylic alcohol
substrate, the correct stereoselectivity was obtained only when the structures were optimized
with a continuum representation of the solvent. The discrepancy between gas phase and
solution data is found to result from a competition between internal stabilization and
solvation of the OH group of the substrate.
Abstract:The intramolecular hydroamination of carbon-carbon p-bonds is an effective method for the rapid construction of nitrogen heterocycles. The rapid evaluation of suitable ligands using virtual screening will aid in the development of a stereoselective analogue of the reaction by predicting effective substrate/ligand combinations. Electronic structure calculations of the relevant transition structures for different nucleophiles and alkynes at the B3LYP/ LACVP* level of theory are presented. They provide the basis for the development of a transition state force field by the Q2MM method, which is discussed in detail. The parameter development and performance for the transition state force field is presented.
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