Organocatalyzed enantioselective aldol reaction of 1H-pyrrole-2,3-diones.

The enantioselective cross aldol reaction of 1-benzyl 4,5-dioxo-2-aryl-4,5-dihydro-1H-pyrrole-3-carboxylates and ketones was studied with proline derivatives or cinchona alkaloid-derived primary amines as the catalysts for the first time. trans-4-Benzoyloxy-L-proline (15) was found to be the best catalyst for acyclic ketones. For cyclohexanone, the best results were achieved with 9-deoxy-9-epi-aminoquinine (18) as the catalyst in the presence of racemic 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (19) as the cocatalyst.

Quinidine thiourea-catalyzed enantioselective synthesis of β-nitrophosphonates: Beneficial effects of molecular sieves.

An efficient method for enantioselective synthesis of β-nitrophosphonates via the Michael addition of diphenyl phosphite to nitroalkenes using the readily available quinidine thiourea organocatalyst has been developed. The desired β-nitrophosphonates were obtained in good ee values. Molecular sieves were found to be crucial for achieving high reproducible yields in this reaction.

Developing novel organocatalyzed aldol reactions for the enantioselective synthesis of biologically active molecules.

Aldol reaction is one of the most important methods for the formation of carbon-carbon bonds. Because of its significance and usefulness, asymmetric versions of this reaction have been realized with different approaches in the past. Over the last decade, the area of organocatalysis has made significant progresses.

Ultrasound promoted selective synthesis of 1,1'-binaphthyls catalyzed by Fe impregnated pillared Montmorillonite K10 in presence of TBHP as an oxidant.

Naphthols were selectively coupled under sonication using Fe(+3) impregnated pillared Montmorillonite K10 and TBHP as an oxidant. Considerable enhancement in the reaction rate was observed under sonication as compared to the reaction performed under silent condition. The activity of catalyst was compared with other Fe clay catalysts.

Ultrasound promoted regioselective nitration of phenols using dilute nitric acid in the presence of phase transfer catalyst.

Phenols are selectively nitrated to o-nitrophenol along with rate enhancement using dilute nitric acid (6 wt%)/tetra butyl ammonium bromide (TBAB) under sonication. The selectivity can also be reversed to p-nitrophenol using NaBr as a catalyst. Kinetic analysis of nitration of phenol both with and without sonication has been investigated by variation of reaction parameters such as catalyst, nitric acid and substrate concentration.