L. Chandrasekhara Rao

“On water” synthesis of highly functionalized 4H-chromenes via carbon–carbon bond formation under microwave irradiation and their antibacterial properties

An ecofriendly and catalyst free synthesis of novel hybrid molecules of chromene and coumarin is described by C–C bond formation in an aqueous medium under microwave irradiation. The methodology provides cleaner conversion, a shorter reaction time and high regio selectivity which makes the protocol globally recognized. For the first time the reaction between a special type of allylic alcohols 2-hydroxy-2H-chromens and 4-hydroxy coumarin to produce novel functionalised 4H-chromenes in excellent yields was achieved and we evaluated their antibacterial properties.

A convenient and rapid microwave-assisted synthesis of spirooxindoles in aqueous medium and their antimicrobial activities

A simple, ecofriendly and one-pot three-component aqueous phase protocol is developed for the synthesis of functionalized spirooxindole derivatives by the reaction of isatin, β-nitrostyrene and benzyl amine/α-amino acids in water under microwave irradiation. The method allows the easy construction of a library of spirooxindoles in moderate to good yields with good diastereoselectivity starting from readily available precursors. In addition, all the synthesized compounds were screened for antimicrobial activity and the majority of compounds showed significant activity against Escherichia coli ATCC 10536, Candida tropicalis ATCC 750, Staphylococcus aureus ATCC25923 and Pseudomonas aeruginosa ATCC 15442.

A domino green method for the rapid synthesis of novel fused isoquinoline derivatives via Knoevenagel/Michael/cyclization reactions on aqueous media and their photophysical properties

An expedient, eco-friendly and green-protocol has been developed for the synthesis of novel 4-imino-2-aryl-4H-pyrido[2,1-a]isoquinoline-3-carbonitrile derivatives via Knoevenagel/Michael/cyclisation reactions in one pot under catalyst-free conditions on aqueous media. These products exhibited UV-Vis absorption and photoluminescence properties.

Reinvestigation of the reaction between 1,3-diketones and 2-hydroxyarylaldehydes: a short, atom-economical entry to tetrahydroxanthenones

A short and facile access to novel functionalized tetrahydroxanthenones via a DABCO-promoted tandem Knoevenagel condensation/hemiketalisation process from easily accessible substrates in a high yield. Tetrahydroxanthenones provide access to the stereo-controlled synthesis of triades or tetrades, which represent privileged structural motifs. Disubstituted tetrahydroxanthenones are generated as a mixture of diastereomers, favoring the formation of selective diastereomers. Unsymmetrical cyclic diketones give mixtures of regio isomers, favoring the formation of sterically less-hindered products.

Microwave assisted novel and regioselective functionalization of imidazopyridines with chromene acetals and β-nitrostyrenes

A facile synthesis of novel functionalized imidazopyridines has been accomplished through the condensation of imidazopyridines with chromene hemiacetals or β-nitro styrenes with high regioselectivity and excellent yields in the presence of a catalytic amount of PTSA or InCl3. In this process, the reaction appears to be very general and suitable for direct functionalization of imidazopyridines. In our present method we successfully achieved regioselectivity.