A new class of bifunctional chiral phase transfer catalysts for highly enantioselective asymmetric epoxidation of α,β-unsaturated ketones at ambient temperature.

A new type of bis-quaternary ammonium bromide as chiral multifunctional phase transfer catalysts derived from readily available inexpensive cinchona alkaloids has been developed and evaluated for the enantioselective asymmetric epoxidation of various chalcones in the presence of lower concentrations of various oxidants, bases, solvents and ambient temperature conditions. Under optimized reaction conditions, highest chemical yields of up to 98% along with the excellent enantioselectivities of about 99% were obtained by using the cinchona based chiral multifunctional phase transfer catalysts. [ABSTRACT FROM AUTHOR]