Tanmoy Chanda - Academia.edu (original) (raw)
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Papers by Tanmoy Chanda
Tetrahedron Letters, 2015
Tetrahedron Letters, 2015
ABSTRACT Quantitative transformation of 3-hydroxyindanones to indenones was achieved via SOCl2 me... more ABSTRACT Quantitative transformation of 3-hydroxyindanones to indenones was achieved via SOCl2 mediated dehydroxylation for the first time. Failure of both acid and base mediated dehydration of 3-hydroxyindanones encouraged us to devise a new protocol involving activation followed by elimination of the hydroxyl group. Thionyl chloride efficiently served the purpose and afforded the desired indenones in excellent yields.
Organic Letters, 2014
A highly efficient and atom-economic dual reaction manifold has been developed to synthesize 4H-t... more A highly efficient and atom-economic dual reaction manifold has been developed to synthesize 4H-thiopyran and 4,5-dihydrothiophene frameworks via regioselective intramolecular C-S fusion of α-allyl-β'-oxodithioesters. The ring size of the sulfur-heterocycles has been efficiently tuned by the use of two different catalytic systems. Palladium activates the Cδ-H of the allyl termini and facilitates the intramolecular Cδ-S coupling to furnish six-membered thiopyran skeletons exclusively. Conversely, the allylic double bond of the same substrate has been activated by BF3·Et2O to promote the Cγ-S cyclization leading to the formation of a five-membered dihydrothiophene nucleus.
European Journal of Organic Chemistry, 2014
RSC Adv., 2014
ABSTRACT A highly efficient and scalable multicomponent domino reaction for the synthesis of func... more ABSTRACT A highly efficient and scalable multicomponent domino reaction for the synthesis of functionalized/annulated quinolines is devised directly from 2-bromoaromatic aldehydes/ketones in H2O–EtOH mixture for the first time. The key to this reaction is the use of an air-stable, eco-efficient and inexpensive CuSO4–D-glucose catalyst system, which is able to catalyze multiple transformations in one pot. The approach is carbon-economic and relies on sequential SNAr/reduction/Friedländer annulation steps, forming C–C and C–N bonds by cleavage of the Csp2–Br bond in a single synthetic operation. The reaction has a broad substrate scope and affords products in good to excellent yields.
![Research paper thumbnail of ChemInform Abstract: Iron-Promoted Domino Annulation of α-Enolic Dithioesters with Ninhydrin under Solvent-Free Conditions: Chemoselective Direct Access to Indeno[1,2-b]thiophenes](https://attachments.academia-assets.com/43972805/thumbnails/1.jpg)
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Tetrahedron Letters
First organocatalytic intramolecular aldolization of ortho-diacylbenzenes to construct highly fun... more First organocatalytic intramolecular aldolization of ortho-diacylbenzenes to construct highly functionalized 3-hydroxyindanones is described. In this transformation a high trans-selectivity is achieved by the use of metal salt of amino acid. This method allows an easy access to the strained spirocyclic 3-hydroxyindanones related to a number of natural product frameworks. Synthesis of a new class of indole skeleton substituted by 3-hydroxyindanones added an extra essence to this new protocol.
Org. Biomol. Chem., 2014
A facile and efficient synthesis of chromen-4-one and isoflavone frameworks is achieved by the do... more A facile and efficient synthesis of chromen-4-one and isoflavone frameworks is achieved by the domino C-acylation/O-acylation/aldolization sequence. This operationally simple one-pot elegant strategy provides structurally unique chromen-4-ones and isoflavones directly from phenols via concomitant formation of multiple C-C and C-O bonds in a single operation. The outcomes of the buttressing effect, substituent dependence, and catalyst and solvent specificity during the course of the Friedel-Crafts acylation reactions are demonstrated and supported by fitting experiments.
Tetrahedron Letters, 2015
Tetrahedron Letters, 2015
ABSTRACT Quantitative transformation of 3-hydroxyindanones to indenones was achieved via SOCl2 me... more ABSTRACT Quantitative transformation of 3-hydroxyindanones to indenones was achieved via SOCl2 mediated dehydroxylation for the first time. Failure of both acid and base mediated dehydration of 3-hydroxyindanones encouraged us to devise a new protocol involving activation followed by elimination of the hydroxyl group. Thionyl chloride efficiently served the purpose and afforded the desired indenones in excellent yields.
Organic Letters, 2014
A highly efficient and atom-economic dual reaction manifold has been developed to synthesize 4H-t... more A highly efficient and atom-economic dual reaction manifold has been developed to synthesize 4H-thiopyran and 4,5-dihydrothiophene frameworks via regioselective intramolecular C-S fusion of α-allyl-β'-oxodithioesters. The ring size of the sulfur-heterocycles has been efficiently tuned by the use of two different catalytic systems. Palladium activates the Cδ-H of the allyl termini and facilitates the intramolecular Cδ-S coupling to furnish six-membered thiopyran skeletons exclusively. Conversely, the allylic double bond of the same substrate has been activated by BF3·Et2O to promote the Cγ-S cyclization leading to the formation of a five-membered dihydrothiophene nucleus.
European Journal of Organic Chemistry, 2014
RSC Adv., 2014
ABSTRACT A highly efficient and scalable multicomponent domino reaction for the synthesis of func... more ABSTRACT A highly efficient and scalable multicomponent domino reaction for the synthesis of functionalized/annulated quinolines is devised directly from 2-bromoaromatic aldehydes/ketones in H2O–EtOH mixture for the first time. The key to this reaction is the use of an air-stable, eco-efficient and inexpensive CuSO4–D-glucose catalyst system, which is able to catalyze multiple transformations in one pot. The approach is carbon-economic and relies on sequential SNAr/reduction/Friedländer annulation steps, forming C–C and C–N bonds by cleavage of the Csp2–Br bond in a single synthetic operation. The reaction has a broad substrate scope and affords products in good to excellent yields.
Tetrahedron Letters
First organocatalytic intramolecular aldolization of ortho-diacylbenzenes to construct highly fun... more First organocatalytic intramolecular aldolization of ortho-diacylbenzenes to construct highly functionalized 3-hydroxyindanones is described. In this transformation a high trans-selectivity is achieved by the use of metal salt of amino acid. This method allows an easy access to the strained spirocyclic 3-hydroxyindanones related to a number of natural product frameworks. Synthesis of a new class of indole skeleton substituted by 3-hydroxyindanones added an extra essence to this new protocol.
Org. Biomol. Chem., 2014
A facile and efficient synthesis of chromen-4-one and isoflavone frameworks is achieved by the do... more A facile and efficient synthesis of chromen-4-one and isoflavone frameworks is achieved by the domino C-acylation/O-acylation/aldolization sequence. This operationally simple one-pot elegant strategy provides structurally unique chromen-4-ones and isoflavones directly from phenols via concomitant formation of multiple C-C and C-O bonds in a single operation. The outcomes of the buttressing effect, substituent dependence, and catalyst and solvent specificity during the course of the Friedel-Crafts acylation reactions are demonstrated and supported by fitting experiments.