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A mild and efficient protocol was developed for the synthesis of pyrazole and 2°-amine hybrid conjugates through an InCl3 Ugi four-component reaction followed by a base mediated secondary amine coupling reaction. MCRs have been used extensively in the field of combinatorial chemistry, which offers the synthesis of libraries of similar molecules in a parallel fashion. A small library of novel N-allyl-N-(1-(4-(aminomethyl) phenyl)-2-(tert-butylamino)-2-oxoethyl)-1,3-diphenyl-1H-pyrazole-4-carboxamide scaffold was designed and synthesized through a one-pot four-component Ugi reaction, the resulting Ugi product pyrazole derivative coupled with various secondary amines to prepare target pyrazole – amine conjugate molecules. The structures of synthesized conjugates confirmed by spectroscopic techniques (NMR, C, H, N analysis, and MS). The in vitro antimicrobial survey of these pyrazole-secondary amine conjugates was supported by DFT studies; thereby notifies the conjugates are promising antimicrobial agents and are comparable to the standard antimicrobial molecules such as ampicilin, griseofulvin, isoniazide and rifampicin.

With the aim to discover potent and novel antitumor agents, a series of thiourea compounds bearing 3-(4-methoxyphenyl)azetidine moiety were designed according to the essential pharmacophoric features of the reported VEGFR-2 inhibitors and synthesized. All the synthesized compounds were evaluated for their in vitro anticancer activity against various human cancer cell lines (lung (A549), prostate (PC3), breast (MCF-7), liver (HepG2), colon (HCT-116), ovarian (SKOV-3), skin (A431), brain (U251) and kidney (786-O)). 3-(4-Methoxy-3-(2-methoxypyridin-4-yl)phenyl)-N-(4-methoxyphenyl)azetidine-1-carbothioamide (3B) was found to be most potent member against PC3, U251, A431, and 786-O cancer cell lines with EC50 values 0.25, 0.6, 0.03, and 0.03 µM, respectively and showed more potency than Doxorubicin in PC3, A431, and 786-O cell lines. Compounds 1B to 7B showed EC50 values ranging from 0.03 to 12.55 µM in A431 cell line. Compound 3-(4-methoxy-3-(pyridin-4-yl)phenyl)-N-(4-methoxyphenyl)azetidine-1-carbothioamide (1B) was found to be highly efficient in A431 and 786-O cell line with EC50 values of 0.77 and 0.73 µM respectively. All the compounds exhibited good to moderate cytotoxic activity. The pharmacophoric features and molecular docking studies confirmed the potentialities of compounds 1B, 2B, 3B and 5B to be VEGFR-2 inhibitors. Moreover, in silico ADMET prediction indicated that most of the synthesized compounds have drug-like properties, possess low adverse effects and toxicity. In addition, the DFT studies for the most active compounds (1B and 3B) were carried out. In the end, our studies revealed that the compounds 1B and 3B represent promising anticancer potentialities through their VEGFR-2 inhibition.

A novel microwave assisted ligand-free palladium-catalyzed post Ugi reaction for the synthesis of isoquinolone and pyrazole mixed pharmacophore derivatives was achieved from isocyanide and pyrazole substituted amide molecules (synthesized by using Ugi reaction). Benzaldehyde, aniline, t-butyl isocyanide and a variety of pyrazole carboxylic acids are being used as starting materials for the Ugi-MCR to generate diverse amide precursors, which in turn provided an access to the synthesis of various isoquinolone-pyrazole hybrid derivatives in moderate to good yields through the isocyanide insertion and successive intramolecular cyclization. The newly synthesized target compounds were characterized by 1H NMR, 13C NMR, HRMS, and elemental analysis. In vitro antimicrobial activity of the prepared molecules was studied against various pathogenic strains; the results obtained were further described with the help of DFT and molecular orbital calculations. Compound 6e and 6g revealed good antimicrobial activity compared to standard drugs kanamycin and amphotericin B.

Aroyl group driven phosphonate-phosphate rearrangement in dialkyl/aryl(α-hydroxy-β-oxo-β-arylethyl)phosphonates having α-proton under basic conditions is presented and extended to a novel one-pot direct coupling method between 2-oxoaldehydes (2OA) and H -phosphonates/diphenylphosphine oxide. The one-pot coupling reaction has an advantage in terms of using commercially available substrates and its broad substrate scope. The reactions between 2OAs and diphenylphosphine oxide represent a unique phosphine oxide-phosphinate rearrangement.

Here we report a practical and efficient method for the synthesis of menaquinone vitamin (K2) analog MK-6 in all trans forms through “1 + 5 convergent synthetic approach” of pentaprenyl chloride with monoprenyl menadione derivative. In the synergistic factors, less efficient leaving group/more efficient nucleophile (Cl) in the substrate makes it more prominent reaction by eliminating all Sn2’ side reaction products. Further, the addition of acetic acid in the last step (desulfonation) of reaction sequence removes the limitations of the reactions in terms of cyclized side product (multiple reactions of pentaprenyl alcohol with Et3B), byproduct (Et3B, incendiary compound) formations and their interruption in the tricky purification processes. The utility of this method was further extended to find an efficient one-pot synthesis to MK-9 to the gram scale synthesis. This approach is economical and efficient and avoids the awkward chromatographic separation processes.

An efficient functional group induced strategy for the synthesis of 6-aminophenanthridines (6AP) has been developed as a result of an in situ generated novel system "CO-CH(N1N2)". This reaction presents a new mode of N2 extrusion in benzotriazoles that later result in decarbonylative cyclization to 6AP. This method offers an easier protocol for the synthesis of 6AP from readily available inexpensive substrates.

The potential of TBHP to promote oxidative hydroxylation of α-hydroxy-β-oxophosphonates (HOPs) through C(CO)–C bond cleavage is described. This cleavage, as depicted in the mechanism, is expected through an isomer of HOP that reacts with TBHP to generate acids.

Given the attractive ability of iminium ions to functionalize molecules directly at ostensibly unreactive positions, the reactivity of iminium ions, in which an α CH2 group is replaced by CO was explored. Background studies on the ability of such iminium cations to promote reactions via an iminium-catalyzed or iminium-equivalent pathway are apparently unavailable. Previously, tandem cross-coupling reactions were reported, in which an iminium ion undergoes nucleophilic 1,2-addition to give a putative three-component intermediate that abstracts a proton in situ and undergoes self-deamination followed by unprecedented DMSO/aerobic oxidation to generate α-ketoamides. However, later it was observed that iminium ions can generate valuable α-ketoamides through simple aerobic oxidation. In all reactions, iminium ions were generated in situ by reaction of 2-oxoaldehydes with secondary amines.

A novel and efficient method for the synthesis of α-ketoamides, employing a dimethyl sulfoxide (DMSO)-promoted oxidative amidation reaction between 2-oxoaldehydes and amines under metal-free conditions is presented. Furthermore, mechanistic studies supported an iminium ion-based intermediate as a central feature of reaction wherein C1-oxygen atom of α-ketoamides is finally derived from DMSO.

Aroyl group driven phosphonate-phosphate rearrangement in dialkyl/aryl(α-hydroxy-β-oxo-β-arylethyl)phosphonates having α-proton under basic conditions is presented and extended to a novel one-pot direct coupling method between 2-oxoaldehydes (2OA) and H -phosphonates/diphenylphosphine oxide. The one-pot coupling reaction has an advantage in terms of using commercially available substrates and its broad substrate scope. The reactions between 2OAs and diphenylphosphine oxide represent a unique phosphine oxide-phosphinate rearrangement.

A variety of functional groups can be introduced in the phenanthridine skeleton following the 3-component strategy shown.

A highly efficient, novel, microwave-assisted, metal-free, diastereoselective synthesis of tetrahydrofuro[3,2-d]oxazole is disclosed. The synthesis of napthoxazoles is achieved for the first time without the aid of an external catalyst. On the contrary, our reactions generated naphthofuranones when treated in the presence of metals in microwave/thermal conditions. The unusual behavior of our reactions has further been explored in the generation of furanones from tetrahydrofuro[3,2-d]oxazole through the use of metals.

Highly efficient catalyst free methods for the synthesis of α-hydroxy-β-oxophosphonates and α-oxoesters have been described. The existence of a 2-oxo group in α-oxoaldehydes is a key factor in promoting the reaction of the tervalent phosphite form towards 2-oxoaldehydes in the synthesis of α-hydroxy-β-oxophosphonates. The in situ activated α-C–H atom of α-hydroxy-β-oxophosphonates sustains aerobic intramolecular nucleophilic displacement in a curious way to produce α-oxoester.

The pyrrolidine-catalyzed aerobic cross-coupling of glyoxals (I) with phenols, naphthols, indoles, and pyrroles as nucleophiles leads to diones (III) [42 examples].

A highly efficient, novel, microwave-assisted, metal-free, diastereoselective synthesis of tetrahydrofuro[3,2-d]oxazole is disclosed. The synthesis of napthoxazoles is achieved for the first time without the aid of an external catalyst. On the contrary, our reactions generated naphthofuranones when treated in the presence of metals in microwave/thermal conditions. The unusual behavior of our reactions has further been explored in the generation of furanones from tetrahydrofuro[3,2-d]oxazole through the use of metals.

An efficient one-pot multi-component synthesis of flavans using perchloric acid supported on silica as a recyclable heterogeneous catalyst has been described. This is the first report of direct one-step construction of a flavan skeleton from a phenolic precursor. The method involves a Knoevenagel-type condensation leading to in situ formation of transient O-quinone methide which further undergoes [4 + 2]-Diels–Alder cycloaddition with styrene to yield a flavan skeleton. The method provides easy access to a wide range of bio-active natural products viz. flavonoids, anthocyanins and catechins.