Dharmendra Das - Academia.edu (original) (raw)
Papers by Dharmendra Das
Beilstein Journal of Organic Chemistry
A simple electrical mortar–pestle was used for the development of a green and facile mechanochemi... more A simple electrical mortar–pestle was used for the development of a green and facile mechanochemical route for the catalyst-free halogenation of phenols and anilines via liquid-assisted grinding using PEG-400 as the grinding auxiliary. A series of mono-, di-, and tri-halogenated phenols and anilines was synthesized in good to excellent yields within 10–15 min in a chemoselective manner by controlling the stoichiometry of N-halosuccinimides (NXS, X = Br, I, and Cl). It was observed that PEG-400 plays a key role in controlling the reactivity of the substrates and to afford better regioselectivity. Almost exclusive para-selectivity was observed for the aromatic substrates with free o- and p-positions for mono- and dihalogenations. As known, the decarboxylation (or desulfonation) was observed in the case of salicylic acids and anthranilic acids (or sulfanilic acids) leading to 2,4,6-trihalogenated products when 3 equiv of NXS was used. Simple instrumentation, metal-free approach, cost-e...
A simple electrical mortar-pestle was used in the development of a green and facile mechanochemic... more A simple electrical mortar-pestle was used in the development of a green and facile mechanochemical route for the catalyst-free halogenation of phenols and anilines via liquid assisted grinding using PEG-400 as the grinding auxiliary. A series of mono-, di-, tri-halogenated phenols and anilines was synthesized in good to excellent yields within 10-15 min in a chemoselective manner by controlling the stoichiometry of N-halosuccinimide (NXS, X = Br, I, Cl). It was observed that PEG-400 plays a key role in controlling the reactivity of the substrates and to afford better regioselectivity. Almost exclusive para-selectivity was observed for the aromatic substrates with free o- and p-positions for mono- and di-halogenations. As known, the decarboxylation (or desulfonation) was observed in the case of salicylic acids, anthranilic acids (or sulfanilic acids) leading to 2,4,6-trihalogenated products when 3 equiv of NXS was used. Simple instrumentation, metal-free approach, cost-effectiveness...
Chemistry – An Asian Journal, 2021
Chiral polyheterocycles are one of the most frequently encountered scaffolds in natural products ... more Chiral polyheterocycles are one of the most frequently encountered scaffolds in natural products and drugs repertoire. A carbo-hydrate-based diversity oriented synthetic (DOS) approach has been employed for gaining access to many structurally diverse and stereochemically complex rigid polyheterocyclic molecules with multiple chiral hydroxyl groups to enhance aqueous solubility. Inexpensive chiral pool of D-Glucose has been judiciously exploited to get access of complex chiral polyheterocyclic structures using inexpensive, common achiral reagents and domino-Knoevenagel hetero-Diels-Alder (DKHDA) reaction as one of the key synthetic tools. Stereochemistry of newly generated stereocenters of polycyclic structures are unambiguously determined through NMR and X-ray crystallographic study. A chemoinformatic comparison (PCA and PMI) with 40 branded blockbuster drugs showed that newly generated polyheterocycles have good three-dimensional scaffold diversity and most of these pass the Lipinski filter of drug-likeness.
RSC Advances, 2021
A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel re... more A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel reaction for the selective detection of hydrazine in solid, liquid and vapour phases.
RSC Advances, 2021
A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel re... more A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel reaction for the selective detection of hydrazine in solid, liquid and vapour phases.
Journal of Heterocyclic Chemistry, 2020
The Journal of Organic Chemistry, 2019
A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed u... more A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed using Pd(II) as catalyst in the absence of phosphine ligands in a ball-mill. The developed protocol is highly C-2 selective and tolerant of structural variations with electronrich and electron-deficient substituents both in the indoles and in the iodoarenes. Arylation is possible in both unprotected indoles and N-protected indoles with electron donating group with former substrate being relatively slower to react and little less yielding. Indoles with deactivated five-membered ring could also take part in the reaction with ease. The scalability of the reaction was demonstrated by conducting the reaction in gram scale. In general, the reactions were achieved in shorter time than the conventional methods.
![Research paper thumbnail of Efficient and “Green” Synthetic Route to Imidazo[1,2-a]pyridine by Cu(II)–Ascorbate-Catalyzed A3-Coupling in Aqueous Micellar Media](https://attachments.academia-assets.com/86542901/thumbnails/1.jpg)
](ACS Omega, 2019
An efficient and environmentally sustainable method for the synthesis of imidazo[1,2-a]pyridine d... more An efficient and environmentally sustainable method for the synthesis of imidazo[1,2-a]pyridine derivatives by domino A 3-coupling reaction catalyzed by Cu(II)− ascorbate was developed in aqueous micellar media in the presence of sodium dodecyl sulfate (SDS). The catalyst, a dynamic combination of Cu(II)/Cu(I), was generated in situ in the reaction mixture by mixing CuSO 4 with sodium ascorbate and aided a facile 5-exo-dig cycloisomerization of alkynes with the condensation products of 2-aminopyridines and aldehydes to afford a variety of imidazo[1,2-a]pyridines in good overall yields. A simple experimental setup, water as the "green" medium, and inexpensive catalyst and auxiliary are some of the merits of this protocol.
Beilstein Journal of Organic Chemistry
A simple electrical mortar–pestle was used for the development of a green and facile mechanochemi... more A simple electrical mortar–pestle was used for the development of a green and facile mechanochemical route for the catalyst-free halogenation of phenols and anilines via liquid-assisted grinding using PEG-400 as the grinding auxiliary. A series of mono-, di-, and tri-halogenated phenols and anilines was synthesized in good to excellent yields within 10–15 min in a chemoselective manner by controlling the stoichiometry of N-halosuccinimides (NXS, X = Br, I, and Cl). It was observed that PEG-400 plays a key role in controlling the reactivity of the substrates and to afford better regioselectivity. Almost exclusive para-selectivity was observed for the aromatic substrates with free o- and p-positions for mono- and dihalogenations. As known, the decarboxylation (or desulfonation) was observed in the case of salicylic acids and anthranilic acids (or sulfanilic acids) leading to 2,4,6-trihalogenated products when 3 equiv of NXS was used. Simple instrumentation, metal-free approach, cost-e...
A simple electrical mortar-pestle was used in the development of a green and facile mechanochemic... more A simple electrical mortar-pestle was used in the development of a green and facile mechanochemical route for the catalyst-free halogenation of phenols and anilines via liquid assisted grinding using PEG-400 as the grinding auxiliary. A series of mono-, di-, tri-halogenated phenols and anilines was synthesized in good to excellent yields within 10-15 min in a chemoselective manner by controlling the stoichiometry of N-halosuccinimide (NXS, X = Br, I, Cl). It was observed that PEG-400 plays a key role in controlling the reactivity of the substrates and to afford better regioselectivity. Almost exclusive para-selectivity was observed for the aromatic substrates with free o- and p-positions for mono- and di-halogenations. As known, the decarboxylation (or desulfonation) was observed in the case of salicylic acids, anthranilic acids (or sulfanilic acids) leading to 2,4,6-trihalogenated products when 3 equiv of NXS was used. Simple instrumentation, metal-free approach, cost-effectiveness...
Chemistry – An Asian Journal, 2021
Chiral polyheterocycles are one of the most frequently encountered scaffolds in natural products ... more Chiral polyheterocycles are one of the most frequently encountered scaffolds in natural products and drugs repertoire. A carbo-hydrate-based diversity oriented synthetic (DOS) approach has been employed for gaining access to many structurally diverse and stereochemically complex rigid polyheterocyclic molecules with multiple chiral hydroxyl groups to enhance aqueous solubility. Inexpensive chiral pool of D-Glucose has been judiciously exploited to get access of complex chiral polyheterocyclic structures using inexpensive, common achiral reagents and domino-Knoevenagel hetero-Diels-Alder (DKHDA) reaction as one of the key synthetic tools. Stereochemistry of newly generated stereocenters of polycyclic structures are unambiguously determined through NMR and X-ray crystallographic study. A chemoinformatic comparison (PCA and PMI) with 40 branded blockbuster drugs showed that newly generated polyheterocycles have good three-dimensional scaffold diversity and most of these pass the Lipinski filter of drug-likeness.
RSC Advances, 2021
A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel re... more A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel reaction for the selective detection of hydrazine in solid, liquid and vapour phases.
RSC Advances, 2021
A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel re... more A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel reaction for the selective detection of hydrazine in solid, liquid and vapour phases.
Journal of Heterocyclic Chemistry, 2020
The Journal of Organic Chemistry, 2019
A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed u... more A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed using Pd(II) as catalyst in the absence of phosphine ligands in a ball-mill. The developed protocol is highly C-2 selective and tolerant of structural variations with electronrich and electron-deficient substituents both in the indoles and in the iodoarenes. Arylation is possible in both unprotected indoles and N-protected indoles with electron donating group with former substrate being relatively slower to react and little less yielding. Indoles with deactivated five-membered ring could also take part in the reaction with ease. The scalability of the reaction was demonstrated by conducting the reaction in gram scale. In general, the reactions were achieved in shorter time than the conventional methods.
ACS Omega, 2019
An efficient and environmentally sustainable method for the synthesis of imidazo[1,2-a]pyridine d... more An efficient and environmentally sustainable method for the synthesis of imidazo[1,2-a]pyridine derivatives by domino A 3-coupling reaction catalyzed by Cu(II)− ascorbate was developed in aqueous micellar media in the presence of sodium dodecyl sulfate (SDS). The catalyst, a dynamic combination of Cu(II)/Cu(I), was generated in situ in the reaction mixture by mixing CuSO 4 with sodium ascorbate and aided a facile 5-exo-dig cycloisomerization of alkynes with the condensation products of 2-aminopyridines and aldehydes to afford a variety of imidazo[1,2-a]pyridines in good overall yields. A simple experimental setup, water as the "green" medium, and inexpensive catalyst and auxiliary are some of the merits of this protocol.