@article {47687, title = {Photoinduced multicomponent regioselective synthesis of 1,4,5-trisubstituted-1,2,3-triazoles: transition metal-, azide- and oxidant-free protocol}, journal = {Advanced Synthesis \& Catalysis}, volume = {363}, year = {2021}, month = {JUL }, pages = {3560-3565}, type = {Article}, abstract = {A transition metal- and azide-free approach is explored to synthesize 1,4,5-trisubstituted-1,2,3-triazoles under sunlight. The reaction proceeds via C-N and N-N bond formations. These regioselective 1,2,3-triazoles are obtained from isatin Schiff bases, benzaldehydes and tosylhydrazine in the presence of base. This protocol offers the structurally diverse 1,2,3-triazole derivatives with 75-90\% yields.}, keywords = {1, 2, 3-triazoles, 4, 5-trisubstituted-1, azide- and oxidant free protocol, Cycloaddition, milder reaction conditions, molecular diversity, Multicomponent reaction, Regioselectivity, transition metal-}, issn = {1615-4150}, doi = {10.1002/adsc.202100321}, author = {Sai Allaka, Bhargava and Basavoju, Srinivas and Rama Krishna, Gamidi} } @article {47834, title = {Silver-catalyzed [3 + 3]-annulation cascade of alkynyl alcohols and α,β-unsaturated ketones for the regioselective assembly of chromanes}, journal = {Organic Chemistry Frontiers}, volume = {9}, year = {2022}, month = {JAN}, pages = {802-809}, type = {Article}, abstract = {An unprecedented Ag(i)-catalyzed [3 + 3]-annulation of alkynyl alcohols (5-hexyn-1-ols) and α,β-unsaturated ketones is reported to construct simple to complex chromanes. This transformation begins with hydroalkoxylation of alkynol through C{\textendash}C triple bond activation to give cyclic-enol ether, followed by intermolecular 1,4-addition and intramolecular 1,2-addition of enol ethers onto the enone and oxidative aromatization or Grob-type elimination steps. Facile reaction conditions, broad substrate scope, good to excellent yields, and atom economy are the salient features of this protocol. Isolation of the active pyran-tethered cyclohexadiene reaction intermediate, additional supporting experiments, and DFT calculations strongly support the experimental findings and corroborate our proposed mechanism.}, issn = {2052-4129}, doi = {10.1039/D1QO01643A}, author = {Nakate, Ashwini K. and Thorat, Sagar S. and Jain, Shailja and Rama Krishna, Gamidi and Vanka, Kumar and Kontham, Ravindar} } @article {48733, title = {Metabolites from lactococcus lactis subsp. lactis: isolation, structure elucidation, and antimicrobial activity}, journal = {ACS Omega}, volume = {8}, year = {2023}, month = {SEP}, pages = {36628-36635}, type = {Article}, abstract = {

Herein, we disclose the identification of novel metabolites from a potential probiotic strain, Lactococcus lactis subsp. lactis, obtained from traditional dairy milk samples collected in Maharashtra, India (in January 2021). Isolated metabolites include pyrazin-2-carboxamide [1, pyrazinamide, a potential antitubercular drug], 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (2, DDMP), 2,4-di-tert-butylphenol (3), and hexadecanoic acid (4, palmitic acid). The chemical structures of these metabolites were elucidated through extensive 1D NMR (H-1 and C-13) and 2D NMR (HSQC, HMBC, and NOESY) analyses, high-resolution mass spectrometry, high-performance liquid chromatography, and single-crystal X-ray crystallography. Furthermore, these novel metabolites exhibited potent inhibitory activities against various bacteria, fungi, and yeast strains with minimum inhibitory concentrations ranging between 1.56 and 25 mu g/mL, and compounds 1 and 3 were found to be most active against a wide range of microbial strains tested.

}, issn = {2470-1343}, doi = {10.1021/acsomega.3c01662}, author = {Navale, Vishwambar D. and Borade, Balasaheb R. and Rama Krishna, Gamidi and Vamkudoth, Koteswara Rao and Kontham, Ravindar} } @article {49053, title = {Base controlled rongalite-mediated reductive aldol/cyclization and dimerization of isatylidene malononitriles/cyanoacetates}, journal = {Organic and biomolecular chemistry}, volume = {22}, year = {2024}, month = {FEB}, pages = {1727-1732}, type = {Article}, abstract = {

In this study, we developed a novel methodology involving a base-controlled, rongalite-mediated reductive/aldol reaction, followed by cyclization of isatylidene malononitriles/cyanoacetates, resulting in the synthesis of spiro[2,3-dihydrofuran-3,3 {\textquoteleft}-oxindole]. Additionally, we have disclosed a rongalite-mediated dimerization process for isatylidene malononitriles, yielding dispiro[cyclopent-3 {\textquoteleft}-ene]bisoxindole. The utilization of rongalite in this reaction serves a dual purpose, acting both as a reducing agent and a C1 synthon. The developed approach has several advantages like a simple reaction setup, a wide substrate scope, requiring less time, using water as a green solvent, no metal or catalyst is required and products can be easily isolated via filtration with excellent yields under mild reaction conditions. A novel methodology was developed for the synthesis of spiro[2,3-dihydrofuran-3,3 {\textquoteleft}-oxindole] and dispiro[cyclopent-3 {\textquoteleft}-ene]bisoxindole under mild reaction conditions using inexpensive reagents.

}, issn = {1477-0520}, doi = {10.1039/d3ob01794j}, author = {Chaudhari, Suryakant S. and Nichinde, Chandrakant B. and Patil, Baliram R. and Girase, Amardipsing S. and Rama Krishna, Gamidi and Kinage, Anil K.} } @article {49024, title = {Bronsted acid-promoted cyclodimerization of α,β-unsaturated γ-ketoesters: construction of fused pyrano-ketal-lactones and γ-ylidene-butenolides}, journal = {ACS Omega}, volume = {9}, year = {2024}, month = {APR }, pages = {19859-19878}, type = {Article}, abstract = {

Unprecedented MsOH-promoted diastereoselective cascade dimerization and intramolecular lactonization of readily accessible alpha,beta-unsaturated gamma-ketoesters are presented. The results obtained in this work, control experiments, and density functional theory (DFT) calculations suggested that the initial enolization and E to Z isomerization/equilibration of olefin (C=C) of substrate alpha,beta-unsaturated gamma-ketoesters give a Z-isomer preferentially over an E-isomer. Subsequently, the Z-isomer undergoes intermolecular annulation with alpha,beta-unsaturated gamma-ketoesters via domino Michael addition/ketalization/lactonization steps to furnish fused tetracyclic pyrano-ketal-lactone. However, the Z-isomer prefers intramolecular trans-esterification in a competing pathway and gives bicyclic gamma-ylidene-butenolide. The key features of this work include simple Br \& oslash;nsted acid catalysis, the formation of three bonds, two rings, and three contiguous stereogenic centers in a single step, DFT calculations, and the assignment of relative stereochemistry through X-ray diffraction (XRD) and two-dimensional (2D) nuclear magnetic resonance (NMR) analyses.

}, issn = {2470-1343}, doi = {10.1021/acsomega.3c08873}, author = {Vinodkumar, Ramavath and Nakate, Ashwini K. and Sharma, Himanshu and Vanka, Kumar and Rama Krishna, Gamidi and Kontham, Ravindar} } @article {49395, title = {Visible-light-induced radical sulfonylative-cyclization cascade of 1,6-Enynol derivatives with sulfinic acids: a sustainable approach for the synthesis of 2,3-disubstituted benzoheteroles}, journal = {CHEMSUSCHEM}, volume = {17}, year = {2024}, month = {OCT }, type = {Journal Article}, keywords = {1, 6-Enynols, Benzofurans, Benzothiophenes, indoles, Sulfones}, issn = {1864-5631}, doi = {10.1002/cssc.202400227}, author = {Haritha Kumari, Arram and Jagadesh Kumar, Jangam and Sharadha, Nunavath and Rama Krishna, Gamidi and Jannapu Reddy, Raju} }