Enantioselective Synthesis of β-(3-Hydroxypyrazol-1-yl) Ketones Using an Organocatalyzed Michael Addition Reaction

Beta-(3-hydroxypyrazol-1-yl) ketones have been prepared in high yields and excellent enantioselectivities (94-98% ee) via a Michael addition reaction between 2-pyrazolin-5-ones and aliphatic acyclic alpha,beta-unsaturated ketones using 9-epi-9-amino-9-deoxyquinine as the catalyst. These results account for the first example of an aza-Michael addition of the ambident 2-pyrazolin-5-one anion to a Michael acceptor.