Asymmetric [3+2] spiroannulation of pyrazolone-derived Morita-Baylis-Hillman carbonates with alkynyl ketones: facile access to spiro[cyclopentadiene-pyrazolone] scaffolds.

A tertiary amine-catalyzed asymmetric [3+2] spiroannulation reaction of pyrazolone-derived Morita-Baylis-Hillman carbonates with alkynyl ketones was achieved under mild conditions. This protocol offers a facile approach to chiral spiro[cyclopentadiene-pyrazolone] scaffolds in good to high yields (up to 92%) with good degrees of enantiocontrol (up to 98% ee). In addition, scale-up reaction and transformation of the products were performed to show the synthetic utility of this protocol.