Chiradeep Panja

Gallium (III) triflate catalyzed efficient Strecker reaction of ketones and their fluorinated analogs

The synthesis of α-aminonitriles and their fluorinated analogs has been carried out in high yield and purity by the Strecker reaction from the corresponding ketones and amines with trimethylsilyl cyanide using gallium triflate in dichloromethane. Monofluoro-, difluro-, or trifluoromethyl groups can be incorporated into the α-aminonitrile product by varying the nature of the fluorinated ketones. Study with various fluorinated and nonfluorinated ketones reveals that the choice of proper catalyst and the solvent system (suitable metal triflates as a catalyst and dichloromethane as a solvent) plays the key role in the direct Strecker reactions of ketones.

BF3-H2O catalyzed hydroxyalkylation of aromatics with aromatic aldehydes and dicarboxaldehydes: efficient synthesis of triarylmethanes, diarylmethylbenzaldehydes, and anthracene derivatives.

BF(3)-monohydrate is found to be an efficient and strong acid catalyst as well as an effective protosolvating medium suitable for the hydroxyalkylation of arenes with aromatic aldehydes. This reaction has been extended to aromatic dialdehydes, such as terephthalic dicarboxaldehyde and isoterephthalic dicarboxaldehyde, for the efficient synthesis of diarylmethylbenzaldehydes, which are useful synthons for various organic transformations. Further, successful one step convergent synthesis of various synthetically useful anthracene derivatives from phthalaldehyde was also achieved. BF(3)-H(2)O is less expensive and acts as an efficient substitute for nonoxidizing strong protic acids/superacids.

Preparation of TMS protected trifluoromethylated alcohols using trimethylamine N-oxide and trifluoromethyltrimethylsilane (TMSCF3)

Abstract A catalytic trifluoromethylation of aldehydes using trimethylamine N -oxide and trifluoromethyltrimethylsilane (TMSCF 3 ) is described. Aromatic, aliphatic and α,β-unsaturated aldehydes provided good to excellent yields of the corresponding trifluoromethylated products.

Effect of carbonates/phosphates as nucleophilic catalysts in dimethylformamide for efficient cyanosilylation of aldehydes and ketones

Cyanosilylation of aldehydes and aliphatic ketones can be carried out in dimethylformamide even without the use of any catalyst. In the presence of nucleophilic catalysts such as carbonate and phosphate salts, the reaction rate is significantly enhanced.

Efficient green synthesis of α-aminonitriles, precursors of α-amino acids

The synthesis of α-aminonitriles by a direct three component Strecker reaction has been achieved using environmentally friendly solid acid catalysts, Nafion®-H and Nafion®SAC-13.

Pinacol coupling of aromatic aldehydes and ketones.. An improved method in an aqueous medium

Reductive coupling of aromatic aldehydes and ketones leading to 1,2-diols has been achieved with high yield and good diastereoselectivity under environmentally friendly conditions using aluminium powder in the presence of aqueous sodium hydroxide. The notable advantage of the present method seems to be the negligible formation of side products arising mainly due to reduction of the carbonyls to the corresponding alcohols, Cannizzaro reaction and formation of olefins via McMurry coupling. Diaryl ketones have been found to be unreactive under the present conditions. Moreover, the aluminium recovered after the reaction can be reused after washing and drying.

Synthesis of Dihydropyrimidinones/Thiopyrimidinones: Nafion-Ga, an Efficient “Green” Lewis Acid Catalyst for the Biginelli Reaction

Biginelli reaction is the most well-known and widely studied multicomponent reaction used for the direct synthesis of many biologically active 3,4-dihydropyrimidinones or thiones and their derivatives by reacting a β-keto ester/1,3-dicarbonyl compound, an aldehyde, and urea/thiourea. A new easily recoverable solid catalyst, Nafion-Ga (Gallium Nafionate, Ga(III) salt of Nafion-H, a solid polymeric perfluoroalkanesulfonic acid) was prepared from Nafion-K by metal exchange. Nafion-Ga is found to be an efficient and environmentally benign catalyst for the Biginelli reaction. A series of 3,4-dihydropyrimidinones and thiones were conveniently prepared by this green protocol using the catalyst under solvent free conditions. The wide scope of the catalyst for many other acid catalyzed organic transformations can be ascertained by further screening studies.Graphical Abstract

Gallium (III) triflate-catalyzed synthesis of heterocycles: quinoxalines, 1,5-benzodiazepines and their fluorinated derivatives

BACKGROUND The quinoxaline nucleus is a part of several antibiotics, such as echinomycin, levomycin and actinomycin, which are known to inhibit the growth of Gram-positive bacteria and are active against various transplantable tumors. Benzodiazepines are important classes of heterocycles that draw significant interest from the pharmaceutical industry because of their prominent therapeutic value, such as antiviral, antibacterial, anti-inflammatory, antiprotozoaval properties and also as kinase inhibitors. They have also been evaluated as anticancer, anthelmintic, antifungal and insecticidal agents. RESULTS & CONCLUSION Quinoxalines, benzodiazepines and their fluorinated derivatives have been prepared in excellent yields from the corresponding diamines and diketones using gallium (III) triflate as an efficient and environmentally friendly catalyst, due to its stability, recyclability and minimal toxicity.