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1. Discovery of benzotriazole and its derivatives as efficient and inexpensive ligands for the coupling reactions and their application in the tandem synthesis of heterocycles/natural products/organic materials
Benzotriazole has been much explored by the Katritzky group as a synthetic auxiliary in a number of transformations due to its interesting properties. We have first time noticed that this air and moisture stable molecule ‘benzotriazole’ has excellent coordination capability which could be favorable for stabilizing catalytic species and assisting the catalytic cycle. We started our journey by using benzotriazole as Ligand for the copper-catalyzed C-N and C-S coupling reaction. Encouraged by preliminary results we have designed a large number of benzotriazole based ligand for the various coupling reactions and observed the designed ligand (hydroxymethyl)benzotriazole was more efficient than benzotriazole for C-N coupling reaction.


Synthetic application: Synthesis of 1,6-Naphthyridines, bisindolo-, and pyrrolo[2,1-a]isoquinolines
We have successfully extended the scope of the developed chemistry for the regioselective tandem synthesis of biologically important Naphthyridines and bisindolo[2,1-a]isoquinolines, a regioisomer of bisindolo[2,1-a]quinolines used as single-crystal field-effect transistor.


2-(1-Benzotriazolyl)pyridine (BtPy): A Novel Inexpensive and Robust Ligand for the Palladium-Catalyzed C-C (Suzuki, Heck, Oxidative-Heck, Sonogashira), C-N and C-S Coupling Reactions:
In continuation of our work on the designing of benzotriazole based ligands for the coupling reactions, recently we have designed an N,N type phosphine free, air stable and robust ligand BtPy by incorporating pyridine ring at N-1 position of the benzotriazole. Results of using this ligand are very interesting and significant. We have first time observed that designed ligand BtPy efficiently catalyzed the Suzuki, Heck, Oxidative-Heck, Sonogashira, Buchwald-Hartwig (C–N), and C–S coupling reactions.


2. Diversity Oriented Synthesis (DOS) of Over Hundred Natural-Product-Likes and p-Conjugated Scaffolds: A Novel Cascade Reaction
Design and synthesis of biologically relevant, drug-like small molecules to perturb and analyze biological systems is one of the main challenges in the medicinal chemistry. Diversity Oriented Synthesis (DOS) of small molecules is new algorithm that enables efficient synthesis of complex molecules. This is one of the most challenging ongoing projects of our laboratory by using electrophilic cyclization chemistry. In this project we have designed a novel cascade synthetic strategy for the “Diversity Oriented Synthesis (DOS) of Over Hundred Heterocyclic/Natural-Product-Likes and p-Conjugated Scaffolds”. Strategy involves the construction of designed scaffolds by the reaction of ortho-akynyaldehydes with appropriate amines/nucleophiles under silver-catalysis by the sequential i) intermolecular C-N bond formation; ii) followed by two intramolecular C/N/O/S-C (attack of nucleophile on imine carbon: intermediate III) and N-C (attack of nitrogen on activated alkyne: intermediate V) bond formation. The mechanism of the designed reaction is well established by the spectroscopic and X-Ray crystallographic studies of the isolated intermediates III, V and the final product VIII. We have successfully synthesized more than 50 distinct heterocyclic scaffolds (>350 distinct novel compounds). It is important to mention that above 25 scaffolds (> 100 novel molecules) were synthesized in water using AgNO3 as a catalyst. The scope of the developed chemistry was successfully extended for the synthesis of sterioselective and diastreoselective molecules. This developed process is expected to find application in organic synthesis/medicinal chemistry/material science in general, and in the construction of a variety of interesting compounds. The preliminary results are very exciting and interesting. Preliminary in-vitro screening results of some scaffolds on cancer cell lines are very impressive.


3. Iodine-mediated chemoselective direct oxidative esterification of aldehydes without affecting alkynes and 10 alcoholic groups: New addition in the functional group transformations
This is another interesting and practically useful novel chemistry being developed in our laboratory. This developed process provides a novel access for the chemoselective synthesis of esters from aldehydes without oxidizing/affecting the primary alcoholic and alkyne group present in the substrate via formation of hypoiodide intermediate. Developed oxidative esterification process, provides a powerful tool for the synthesis/preparation of wide range functionalized pyranoquinolinones, isocoumarins, a-pyranones and natural products. Process is a useful addition in the organic functional group transformations where protection and deprotection is required. Note: This chemistry has been successfully implemented in the M.Sc practical as a green practical.


4. Site-selective electrophilic cyclization and subsequent ring opening: An efficient route to pyrrolo[1,2-a]quinolines and indolizines
An efficient strategy for the synthesis of pyrrolo[1,2-a]quinolines and indolizines from pyranoquinolines via site-selective electrophilic cyclization and subsequent opening of pyran ring using silver/iodine under mild reaction conditions is described. This approach involves preferential attack of pyridyl nitrogen over aryl ring and leads to the formation of 5-endo-dig cyclized products. Quantum chemical calculations between C-N (?Ea = 9.01 kcal/mol) and C-C (?Ea = 31.31 kcal/mol) bond formation were performed in order to rationalized the observed site selectivity. Structure of the products was confirmed by X-ray crystallographic studies. Iodine substituted compounds generated by the electrophilic iodocyclization were further diversified via Pd-catalyzed cross-coupling reactions.


5. Palladium-catalyzed regioselective [3+2] annulation of internal alkynes and iodo-pyranoquinolines with concomitant ring opening: Efficient approach for the synthesis of pyrrolo[1,2-a]quinolines and acridones
A regioselective tandem synthesis of highly functionalized pyrrolo[1,2-a]quinolines has been developed through a novel strategy by palladium-catalyzed [3+2] annulation of iodo-pyranoquinolines and internal alkynes with subsequent ring opening. This chemistry was successfully extended for the synthesis of diverse pharmaceutically important pyrrolo-acridinone via [3+2] annulations/ring opening and successive intramolecular cross-aldol condensation. It is noteworthy, that unsymmetrical internal alkynes containing propargyl alcoholic group, selectively afforded single isomer. Further investigation of the scope and synthetic applications of the present strategy are currently underway and will be reported in due course.

Congratulations to Kapil Mohan Saini whose paper entitled "Transition-Metal-Free Reverse Reactivity of (2-alkynyl)-Arylaldimines: Assembly of Functionalized Amino-Indinones in Chem. Eur. J....Latest


Congratulations to Dr. Pawan K. Mishra. He is selected Sailife-NOST Best Thesis Award 2019


Congratulations to Pradeep Kumar, Vineeta Garg whose paper entitled "Rh(III)-Catalyzed Alkynylation: Synthesis of Functionalized Quinolines from Aminohydrazones "has been published in Chem. Commun.


Congratulations to Dr. Trapti Aggarwal whose review article entitled "Recent advances in the synthesis of carbazoles from indoles" has been published in Org. Biomol. Chem.