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

Asymmetric synthesis of pyrazoles and pyrazolones employing the reactivity of pyrazolin-5-one derivatives

The various catalytic asymmetric strategies employing organo- and metal-catalysts utilized pyrazolin-5-one derivatives for the synthesis of potentially bioactive enantiopure pyrazoles and pyrazolones are presented.

Phosphine-catalyzed [4 + 2] cycloaddition of unsaturated pyrazolones with allenoates: a concise approach toward spiropyrazolones

Phosphine-catalyzed [4 + 2] cycloaddition of unsaturated pyrazolones with allenoates providing concise access to spiropyrazolones.

Zinc chloride catalyzed stereoselective construction of spiropyrazolone tetrahydroquinolines via tandem [1,5]-hydride shift/cyclization sequence

A concise synthesis of spiropyrazolones has been developed via an efficient ZnCl₂-catalyzed stereoselective 1,5-hydride shift/cyclization sequence.

Streocontrolled construction of six vicinal stereogenic centers on spiropyrazolones via organocascade Michael/Michael/1,2-addition reactions

A highly stereoselective one-pot procedure for the synthesis of spiropyrazolone derivatives bearing six contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential catalysis by two organocatalysts, a cinchona-derived aminosquaramide and DBU, a series of diversely functionalized spiropyrazolones are obtained in good yields (47-62%) and excellent stereoselectivities (up to >25:1 dr and 98-99% ee). The opposite enantiomers of the spiropyrazolones are also accessible by employing a pseudoenantiomeric aminosquaramide catalyst.

Catalytic asymmetric 1,2-addition of α-isothiocyanato phosphonates: synthesis of chiral β-hydroxy- or β-amino-substituted α-amino phosphonic acid derivatives

α-Amino phosphonic acid derivatives are considered to be the most important structural analogues of α-amino acids and have a very wide range of applications. However, approaches for the catalytic asymmetric synthesis of such useful compounds are very limited. In this work, simple, efficient, and versatile organocatalytic asymmetric 1,2-addition reactions of α-isothiocyanato phosphonate were developed. Through these processes, derivatives of β-hydroxy-α-amino phosphonic acid and α,β-diamino phosphonic acid, as well as highly functionalized phosphonate-substituted spirooxindole, can be efficiently constructed (up to 99 % yield, d.r. >20:1, and >99 % ee). This novel method provides a new route for the enantioselective functionalization of α-phosphonic acid derivatives.