Asymmetric sequential annulation/aldol process of 4-isothiocyanato pyrazolones and allenones: access to novel spiro[pyrrole–pyrazolones] and spiro[thiopyranopyrrole–pyrazolones]

Abstract

A catalytic asymmetric sequential annulation/aldol reaction of 4-isothiocyanato pyrazolones and allenyl ketones has been developed, which furnished a series of spiro[pyrrole-pyrazolone] heterocycles and structurally novel spiro[thiopyranopyrrole-pyrazolone] derivatives in good yields with high to excellent enantioselectivities. Notably, parallel resolution of racemic spiro[pyrrole-pyrazolones] was achieved by a catalyst-controlled asymmetric intramolecular vinylogous aldol process. Structure diversity of the product was further enhanced by ready transformations.