Core Scaffold-Inspired Stereoselective Synthesis of Spiropyrazolones via an Organocatalytic Michael/Cyclization Sequence

Herein, the organocatalytic asymmetric Michael/cyclization sequence of alpha-isothiocyanato imides and esters with a variety of unsaturated pyrazolones is presented, in general, affording functionalized spiropyrazolones containing three contiguous stereogenic centers in high levels of diastereo- and enantioselectivity (up to 20:1 dr and 99% ee). Moreover, the current protocol provides a highly efficient and convenient strategy that allows rapid enantioselective construction of diversely spiropyrazolone skeletons with high optical purity.