Direct Catalytic Enantioselective Vinylogous Aldol Reaction of Allyl Ketones to Pyrazole-4,5-diones

The first catalytic
enantioselective vinylogous nucleophilic addition
to pyrazole-4,5-diones is reported. Using quinine-derived bifunctional
tertiary amino-amide as the catalyst, this direct aldol reaction of
allyl ketones is shown to proceed exclusively in γ- and E-selective manner to generate pyrazolone derivatives, bearing
an oxygen-containing quaternary stereogenic center, in good yields
with moderate to high enantioselectivities (up to 97:3 er).