| Further development of an organocatalytic LUMO-lowering activation strategy utilizing chiral imidazolidinone salts has been described. Enantioselective catalytic Friedel-Crafts alkylations of furans and thiophenes have been achieved with good yields and high levels of enantioselectivity. Furthermore, this methodology has been utilized to access enantioenriched alpha-chiral esters.; The organocatalytic iminium activation strategy has been applied to the development of an enantioselective Mukaiyama-Michael reaction for the construction of the gamma-butenolide architecture. This reaction is viable due to imidazolidinone catalysts' ability to partition silyloxyfurans to react through an unprecedented 1,4-addition manifold to alpha,beta-unstaturated aldehydes. This Mukaiyama-Michael methodology has also been extended to provide access to alpha-amino acids by use of silyloxyoxazoles.; Enamine activation of aldehydes has provided the first direct asymmetric alpha-oxidation of carbonyls. This proline catalyzed HOMO-raising activation strategy affords high levels of reaction efficiency and enantioselectivity. Moreover, the function of proline solubility has been investigated to explain an unusual kinetic and enantioselective profile.; The imidazolidinone framework, developed for iminium activation, was also demonstrated to participate in enamine activation of aldehydes to perform the enantioselective alpha-chlorination of aldehydes. A first generation catalyst provided good yields and high enantioselectivities at -30°C. Design of a second generation catalyst afforded high levels of reaction efficiency and enantioselectivity at ambient temperature. |
