Rajiv Trivedi

Efficient synthesis, structural characterization and anti-microbial activity of chiral aryl boronate esters of 1,2-O-isopropylidene-α-D-xylofuranose.

A simple and efficient synthetic approach toward a series of chiral aryl boronate esters, starting from D-xylose, as anti-microbial agents, is described herein. Minimum inhibitory concentration and zone of inhibition revealed that these derivatives exhibit potent anti-bacterial and anti-fungal properties. Herein, we report the first anti-microbial activity of this class of compounds. All products have been characterized by NMR ((1)H, (13)C and (11)B), IR, elemental and mass spectral study.

Synthesis, characterization and cytotoxic activity of palladium (II) carbohydrate complexes

AbstractCarbohydrate containing pyridyl triazole ligands, 5-deoxy-1,2-O-isopropylidene-5-(4-(2-pyridyl)-1H-1,2,3-triazole-1-yl)-α-D-xylofuranose (2a), 3-O-Benzyl-5-deoxy-1,2-O-isopropylidene-5-(4-(2-pyridyl)-1H-1,2,3-triazol-1-yl)-α-D-xylofuranose (2b), methyl-5-deoxy-2,3-O-isopropylidene-5-(4-(2-pyridyl)-1H-1,2,3-triazol-1-yl)-β-D-ribofuranoside, (2c) and 6-deoxy-1,2:3,4-di-O-isopropylidene-6-(4-(2-pyridyl)-1H-1,2,3-triazol-1-yl)-α-D-galactopyranose (2d) were prepared by the ‘click’ reaction of 2-ethynyl pyridine with the corresponding azides. The palladium complexes were synthesised by the reaction of pyridyl triazole ligands with [Pd(COD)Cl2] in dichloromethane. All the compounds were characterised by NMR, IR, mass and elemental analysis. Structural characterization of the ligand 2a was done by X-ray crystallography. The ligands and complexes were tested for their cytotoxic activity on different cell lines like A549 (human alveolar adenocarcinoma cells), Neuro2a (mouse neuroblastoma cells), HeLa (cervical carcinoma cancer cells), MDA-MB-231 (human breast adenocarcinoma cells) and MCF7 (human breast adenocarcinoma cells). The complexes showed considerable cytotoxicity while the ligands were non-toxic on the tested cell lines. Graphical AbstractPyridyl-carbohydrate triazole ligands were prepared by means of Cu(II) catalysed 1,3-dipolar cycloaddition reaction. Palladium (II) complexes were prepared by treating these ligands with [Pd(COD)Cl2]. The ligands and their palladium complexes were studied for their cytotoxic activity.

An expedient microwave assisted regio- and stereoselective synthesis of spiroquinoxaline pyrrolizine derivatives and their AChE inhibitory activity

In this study, we report an efficient four-component cascade protocol to afford spiro indeno[1,2-b]quinoxaline-11,3′-pyrrolizines via the condensation of ninhydrin, phenylenediamine, proline, and nitrostyrene derivatives under microwave irradiation and classical conditions. The 1,3-dipolar cycloaddition reaction was found to proceed in a highly regio- and stereoselective manner. This methodology exemplifies the green chemistry protocol for the preparation of spiro-pyrrolizines. In addition, all the synthesized compounds were screened for AChE inhibitory activity and 6 out of 21 compounds depicted significant activity in the low micromolar IC50 range.

VCl3‐Catalyzed Selective Oxidation of Sulfides to Sulfoxides Using H2O2 as Oxidant

Abstract VCl3 is an effective catalyst for the catalytic oxidation of sulfides to afford sulfoxides in good yields using hydrogen peroxide as an oxidant.

Asymmetric Mannich reaction: highly enantioselective synthesis of 3-amino-oxindoles via chiral squaramide based H-bond donor catalysis

We describe here a simple and facile asymmetric Mannich reaction catalyzed by chiral Cinchona alkaloid based squaramide containing H-bond donor catalysts, wherein, the reaction of 1,3-diketones with isatin (N-Boc) ketimines led to the formation of 3-aminooxindole derivatives. These derivatives were obtained in high yields with excellent enantioselectivities under mild conditions using 3 mol% of the catalyst. This protocol provides valuable and easy access to chiral 3-substituted 3-aminooxindole derivatives.

(4-Ferrocenylphenyl)propargyl ether derived carbohydrate triazoles: influence of a hydrophobic linker on the electrochemical and cytotoxic properties

In this article we describe a detailed study of the influence of a hydrophobic linker on the properties of a series of ferrocene–carbohydrate conjugates. The alkyne, (4-ferrocenylphenyl)propargyl ether, was prepared from the reaction of propargyl bromide and 4-ferrocenylphenol. The structure of the alkyne was determined using a single crystal X-ray diffraction study. A benzyl triazole (3a) was synthesised for comparison purposes in the electrochemical and cytotoxic study. Herein, we report the synthesis and characterization of a series of carbohydrate triazole conjugates (3b–h) by using the Huisgen 1,3-dipolar cycloaddition reaction of a series of carbohydrate azides and (4-ferrocenylphenyl)propargyl ether. UV-visible spectroscopy and electrochemical studies were performed on the alkyne and triazole compounds. The data generated from the cyclic voltammetric studies was used to calculate the diffusion coefficients (Df) of the ferrocene–carbohydrate conjugates in DMSO and DMSO–buffer solutions. Slightly higher diffusion coefficient values were obtained for the carbohydrate triazole conjugates (3b–h) in the buffer solution, perhaps due to the hydrophobic nature of the linker and the absence of a hydrogen-bonding substituent adjacent to the ferrocene core. Furthermore, the triazole conjugate (3f) derived from ribofuranose exhibited significant cytotoxicity against a hormone dependent breast cancer cell line (MCF-7) with an IC50 value lower than 10 μM.

Catalysis of the Heck-type reaction of alkenes with arylboronic acids by silica-supported rhodium: an efficient phosphine-free reusable catalytic protocol

A 3-aminopropyl-functionalized silica-supported rhodium(0) catalyst (SiO2–Rh0) was prepared and employed in the Heck-type coupling of arylboronic acids and alkenes, affording good-to-excellent yields of substituted alkenes; the catalyst was recovered by filtration and reused for several cycles.

Synthesis, Structure and Photophysical Properties of Ferrocenyl or Mixed Sandwich Cobaltocenyl Ester Linked meso‐Tetratolylporphyrin Dyads

We report here the design and synthesis of porphyrin–metallocene dyads consisting of a metallocene [either ferrocene or mixed sandwich η5‐[C5H4(COOH)]Co(η4‐C4Ph4) connected via an ester linkage at meso phenyl position of either free‐base or zinc porphyrin. All these dyad systems were characterized by various spectroscopic and electrochemical methods. A dimeric form of this molecule was observed in the X‐ray crystal structure of Zn‐TTPCo. The absorption spectra of all four dyads indicated the absence of electronic interactions between porphyrin macrocycle and metallocene in the ground state. However, interestingly, in all four dyads, fluorescence emission of the porphyrin was quenched (19–55%) as compared to their monomeric units. The quenching was more pronounced in ferrocene derivatives rather than cobaltocenyl derivatives. The emission quenching can be attributed to the excited‐state intramolecular photoinduced electron transfer from metallocene to singlet excited state of porphyrin and the electron‐transfer rates (kET) were established in the range 1.51 × 108 to 1.11 × 109 s−1. They were found to be solvent dependent.

Vanadyl(IV) Acetate: An Efficient, Reusable Heterogenous Catalyst for Aza-Michael Reaction Under Solvent-Free Conditions

Abstract Vanadyl(IV) acetate [VO(OAc)2] efficiently catalyzes the conjugate addition of aliphatic, aromatic amines to α,β-unsaturated carbonyl compounds in solvent-free media at room temperature to afford corresponding amino compounds in good to excellent yields. The catalyst can be recovered and reused for further cycles.

Highly efficient regio and diastereoselective synthesis of functionalized bis-spirooxindoles and their antibacterial properties

A simple, efficient, regioselective and diastereoselective method has been developed for the synthesis of diversely functionalized spirooxindole-pyrrolidines using 0.5 mol% of ceric ammonium nitrate in aqueous medium. All the new compounds are tested for in vitro antimicrobial activity. All the synthesized products have shown good antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Micrococcus luteus (Gram-positive organisms), Salmonella paratyphi, Pseudomonas aeruginosa and Salmonella typhi (Gram-negative organism).