Sai U | Indian Institute of Chemical Technology (original) (raw)

Papers by Sai U

Polystyrene‐supported N,N‐dimethylethylenediamine Pd(II) complex C was used as an efficient catal... more Polystyrene‐supported N,N‐dimethylethylenediamine Pd(II) complex C was used as an efficient catalyst for the synthesis of aromatic ketones via ortho‐acylation of sp 2 C─H bonds of 2‐arylpyridines with alcohols as effective coupling partners. The alcohols were oxidized with tert‐butyl hydroperoxide to their corresponding alde-hydes in situ and efficiently coupled with 2‐arylpyridines to form aryl ketones under solvent‐free conditions. Furthermore, catalyst C could be easily recovered by simple filtration and reused for five cycles without any significant decrease in its activity.

An efficient copper and solvent free Sonogashira cross-coupling reaction catalyzed by polymer sup... more An efficient copper and solvent free Sonogashira cross-coupling reaction catalyzed by polymer supported 3-benzoyl-1-(1-benzylpiperidin-4-yl)-2-thiopseudourea-Pd(II) complex 4 (PS-bpt-Pd) was reported. This inexpensive and simply synthesized heterogeneous catalyst 4 afforded excellent yields of the cross-coupling products under mild reaction conditions. We have achieved high yields for aryl iodide coupling reactions with terminal alkynes at room temperature under copper and solvent-free conditions. In addition, we also observed moderate to good yields for aryl bromides as coupling partner. This insoluble PS-bpt-Pd(II) catalyst 4 can be easily recovered by simple filtration and reused up to five times with stable catalytic activity. In addition to this, heterogeneous Pd (II) complex is even applicable on a gram scale for cross-coupling with high catalytic efficiency.

A recyclable polymereanchored Pd(II) complex C was synthesized and characterized using different ... more A recyclable polymereanchored Pd(II) complex C was synthesized and characterized using different spectroscopic techniques. In addition the catalytic efficiency of the Pd (II) complex C was evaluated for ortho-acylation of 2-aryl pyridines with toluene derivatives to form aryl ketones via cross dehydrogen-ative coupling. In this catalytic process toluene acts as an effective coupling partner upon sp 3 CeH bond oxidation for sp 2 CeH bond acylation of 2-aryl pyridines in the presence of Pd(II)/TBHP system on water. Furthermore, the catalyst C was highly stable and could be easily recovered and reused for four cycles with no significant decrease in its activity and selectivity.

A series of C(3)-trifluoromethylated compounds derived from N-substituted isatins were synthesize... more A series of C(3)-trifluoromethylated compounds derived from N-substituted isatins were synthesized. The biological activity of all 3-hydroxy-3-(trifluoromethyl)indolin-2-one derivatives have been evaluated for in vitro cytotoxic activity and antibacterial activity. The active compounds were screened against nuclear xenobiotic receptor CAR (PDB ID: 1XLS), PIM1 kinase (PDB ID: 2O65), and CDK2 kinase (PDB ID: 3QHR) by using in silico molecular docking studies to obtain lead molecules. In addition to its potential anti-cancer activity, 5-bromo-3-ethynyl-3-hydroxy-1-(prop-2-yn-1-yl)indolin-2-one also showed specific antibacterial activity against S. aureus. Graphical abstract N HO O CF 3 R 1 R = benzyl, ethyl, methyl, allyl, propargyl, phenyl R 1 = chloro, bromo, iodo R

A new polystyrene supported N-phenylpiperazine–Cu(II) complex 4c was found to be an efficient, si... more A new polystyrene supported N-phenylpiperazine–Cu(II) complex 4c was found to be an efficient, simple, versatile catalyst for the selective multicomponent reaction of terminal alkynes, ketones, and secondary amines to give the corresponding propargylamines. The coupled products were formed in excellent yields at low catalyst loadings (0.2 mol% of metal) under solvent free conditions at 110 1C. Further, this heterogeneous catalyst showed excellent recyclability without any significant loss in its activity for up to five times of cycling.

N,N,O-Tridentate palladium(II) complexes [Pd(OAc){R-C 4 H 8 N 2 (CH 2 Ar)}] (R = Ph, Ar = 4-tBu-C... more N,N,O-Tridentate palladium(II) complexes [Pd(OAc){R-C 4 H 8 N 2 (CH 2 Ar)}] (R = Ph, Ar = 4-tBu-C 6 H 3 –OH (4a)) and [2,4-di-tBu-C 6 H 2 –OH, R = benzyl (4b)] 4a and 4b have been synthesized from the corresponding 2-((4-arylpiperazin-1-yl)methyl)phenol ligands 3a and 3b in quantitative yields. The synthesized ligands and their palladium(II) complexes were characterized by NMR, IR and HRMS analyses. Complex 4a has been used as an efficient catalyst for the Suzuki cross-coupling reaction of 5-iodovanillin and 5-bromosalicylaldehyde with various arylboronic acids in low catalytic amounts (0.01–0.05 mol% of 4a). Moreover, this catalytic system is even applicable for Suzuki coupling reactions of deactivated aryl bromides and aryl chlorides, affording the cross-coupling products in good to excellent yields with a broad substrate scope.

Hypervalent iodine(III)/TEMPO-mediated C(sp 3 ), C(sp 2 ) C-H bond oxidation of different oxindol... more Hypervalent iodine(III)/TEMPO-mediated C(sp 3 ), C(sp 2 ) C-H bond oxidation of different oxindole and indole derivatives to their corresponding isatin derivatives was successfully achieved with excellent yields at room temperature. This metal-free method provides a direct access to potential synthon isatin that could be applied in the total synthesis of several biologically active natural products.

A new salen type N ,N-1,2-phenylenebis(3-(4-fluorobenzoyl-2-benzyl-2-thiopseudourea) functionaliz... more A new salen type N ,N-1,2-phenylenebis(3-(4-fluorobenzoyl-2-benzyl-2-thiopseudourea) functionalized polystyrene resin supported palladium(II) complex (3) was found to be highly efficient catalyst for the Suzuki cross-coupling reaction of aryl halides with arylboronic acids. The coupled products of various activated and deactivated aryl halides were produced in good to excellent yields under low catalyst loadings and in water/methanol system. Further, the catalyst showed excellent recyclability without any significant loss in its activity.

A series of N,N 0 -mono substituted acyclic thiourea ligands are found to be highly active phosph... more A series of N,N 0 -mono substituted acyclic thiourea ligands are found to be highly active phosphine-free catalysts for palladium catalyzed Heck reaction of aryl iodides and bromides with olefins. We have achieved high turnover numbers for aryl iodides with olefins (TONs up to 970,000 for the reaction of iodobenzene with styrene).

A new polystyrene supported thiopseudourea palladium(II) complex (3) is found to be a highly acti... more A new polystyrene supported thiopseudourea palladium(II) complex (3) is found to be a highly active catalyst for the copper-free Sonogashira, Suzuki, Heck, Hiyama and Larock heteroannulation reactions of aryl halides. All the reactions proceeded well affording the corresponding cross-coupling products in good to excellent yields. Further, the catalyst showed excellent recyclability without any significant loss in its activity.

We examined the Pd-catalyzed heteroannulation of 2-haloamines with internal alkynes under phosphi... more We examined the Pd-catalyzed heteroannulation of 2-haloamines with internal alkynes under phosphinefree conditions. The thiopseudourea palladium(II) complex found to be an efficient catalyst for the Pd induced heteroannulation. Achieved high turnover number for the heteroannulation reactions of internal alkynes with 2-iodoaniline. A variety of 2-bromoanilines and N-tosyl substituted 2-bromoanilines effectively reacted with different substituted internal alkynes to give the corresponding indoles in good to high yields (1:1 ratio of regioisomers).

Copper-aluminium hydrotalcite (CuAl-HT)/K 2 CO 3 has been employed in the activation of various b... more Copper-aluminium hydrotalcite (CuAl-HT)/K 2 CO 3 has been employed in the activation of various benzyl alcohols with benzylamines to afford the corresponding amines in good to high yields. Experimentation showed that the reaction takes place through sequential transformations: the oxidation of alcohols into carbonyl compounds, imine formation between amines and carbonyl compounds, and then reduction of

A novel, efficient, eco-friendly "on water" method has been developed for the Henry reaction of i... more A novel, efficient, eco-friendly "on water" method has been developed for the Henry reaction of isatins with nitromethane to afford 3-hydroxy-3-nitromethylindolin-2-ones. An enhancement in reaction rate was observed "on water" under mild and catalyst-free conditions. This reaction tolerated a wide range of substrates with good to excellent product yields and is even applicable at large scales. Moreover, this method is environmentally friendly as it reduces the waste generated by the use of toxic solvents.

A series of 3-indolyl-3-hydroxy oxindole derivatives (n ¼ 41) were synthesized by the green amino... more A series of 3-indolyl-3-hydroxy oxindole derivatives (n ¼ 41) were synthesized by the green aminocatalytic method with excellent yields under mild reaction conditions. All the newly synthesized derivatives were subjected to evaluate their cytotoxic properties against different human cancer cell lines. Results indicated that about 73% of the derivatives exhibited significant anti-proliferative activities against leukemia (U937, THP-1), lung (A549) and breast cancer (MCF7) cell lines. Among them a few of the derivatives exhibited the most potent and effective cytotoxic activities on U937 (34, 36, 38 and 41) and MCF7 (12, 35, 40 and 41) cell lines, and their anti-proliferation activities are better than the positive control, Etoposide.

An efficient green protocol has been developed for the synthesis of 3-hydroxy-3-(1H-tetrazol-5-yl... more An efficient green protocol has been developed for the synthesis of 3-hydroxy-3-(1H-tetrazol-5-yl)indolin-2-ones and 3-(phenylamino)-3-(1H-tetrazol-5-yl)indolin-2-ones as a novel class of oxindole derivatives by metal-free azide-nitrile [2 + 3] cycloaddition with excellent yields.

The direct catalytic enantioselective Henry (nitroaldol) reaction of isatins with nitromethane ha... more The direct catalytic enantioselective Henry (nitroaldol) reaction of isatins with nitromethane has been developed in the presence of a biscinchona alkaloid as a chiral organocatalyst. The resulting Henry adducts bearing C3-quaternary stereocentres were obtained in high yields (up to 94%) with high enantioselectivities (up to 97% ee).

Vicinal di-oxygenation of styrene-type olefins was achieved with cheaper, less toxic CuI in the p... more Vicinal di-oxygenation of styrene-type olefins was achieved with cheaper, less toxic CuI in the presence of L-proline as ligand and NaIO 4 as the oxidant. This approach provides a straightforward and efficient access to mono-acylated diols from both styrene and stilbene derivatives with good to excellent yields and diastereoselectivity.