Nickel-catalyzed asymmetric transfer hydrogenation of unsaturated C=C and C=N bonds using formic acid
Date of Issue2017-06-08
School of Physical and Mathematical Sciences
This thesis describes my work on nickel-catalyzed asymmetric transfer hydrogenation of unsaturated C=C and C=N bonds using formic acid. It contains three main parts. Chapter one reports a highly enantioselective asymmetric hydrogenation of hydrazones with a chiral ligand, (S)-Binapine. Both aryl and aliphatic methyl hydrazones afforded the desired products in good to excellent ee values. Furthermore, DFT calculation revealed that the nickel catalyst controls the asymmetric hydride insertion to unsaturated C=N bonds by controlling the binding conformation of the amide directing group, instead of differentiating group on the imine fragment. Chapter two describes asymmetric reductive amination of simple ketones with sulfonamides in one pot. With a nickel/(S)-Binapine catalytic system, a series of chiral tosylamines were obtained in high enantioselectivities. This one-pot reductive amination of simple ketones is operationally simple and avoids the isolation and purification of the intermediate tosylimines. Chapter three reports the asymmetric hydrogenation of olefins for the synthesis of unnatural amino acid derivatives, using a nickel catalyst ligated by a chiral bisphosphine (S)-Binapine. In some cases of cyclic tetra-substituted dehydroamino acid derivatives, good yields and excellent ee values were achieved.