Novel Pyrazole Derivatives Having Mono/Di Chiral Centered Group as Organocatalyst for Henry Reaction

Abstract

The chiral substituted pyrazole-3-carboxamides (4a-c), pyrazole-3-carboxylates (5a-c), pyrazole-3-thioureides (7a-c) and pyrazole-3,4-dicarboxamides (10a-c) were prepared via the pyrazolo-3-chlorocarbonyl 2, pyrazolo-3,4-dicarboxy methyl ester 3 with pyrazole-3-isothiocyanate 6 with different (R)-chiral amino alcohols. All of the synthesized chiral compounds binding a pyrazole skeleton were investigated as organocatalysts for asymmetric aldol reactions between nitromethane and p-nitrobenzaldehyde in the presence of CuCl. Enantiomeric excesses and the reaction yields were found to be appropriate values. Furthermore, the best organocatalyst applied in this study was identified after careful optimization of conditions. Lastly, all of the novel compounds were subjected to computational analysis at the B3LYP/6-31++G(d,p) level of theory to obtain information about their structural and electronic properties.

Keywords

• asymmetric catalyst, chirality, chiral amino alcohol, lewis acid, pyrazole