Browsing by Author "Janardhanan, J.C."

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Functionalizable 1H-Indazoles by Palladium Catalyzed Aza-Nenitzescu Reaction: Pharmacophores to Donor-Acceptor Type Multi-Luminescent Fluorophores
(2018) Janardhanan, J.C.; Mishra, R.K.; Das, G.; Sini, S.; Jayamurthy, P.; Suresh, C.H.; Praveen, V.K.; Manoj, N.; Babu, B.P.
Development of small-molecule-based multi-luminescent fluorophores utilizing simple synthetic methodologies, as well as easily available starting materials, has gained much attention in recent years. Herein, we disclose an efficient protocol for the synthesis of N-protected 1H-indazole derivatives with diverse substituents at their 3- and 5-positions via palladium-catalyzed reactions of hydrazones and p-benzoquinones. The obtained 1H-indazole derivatives can be easily modified into donor-acceptor (D?A)-type chromophores (Indazo-Fluors) with tunable emission properties in both solid and solution state. Owing to the extent of intramolecular charge transfer, Indazo-Fluors exhibit positive solvatochromic emission spanning from blue-green to orange-red. Theoretical studies were undertaken to rationalize the observed trends in the optical properties of Indazo-Fluors. Finally, a triethylene glycol (TEG) appended Indazo-Fluor exhibiting a large Stokes shift and low cytotoxicity allowed us to use it for cell imaging. 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Functionalizable 1H-Indazoles by Palladium Catalyzed Aza-Nenitzescu Reaction: Pharmacophores to Donor-Acceptor Type Multi-Luminescent Fluorophores
(Wiley-VCH Verlag info@wiley-vch.de, 2018) Janardhanan, J.C.; Mishra, R.K.; Das, G.; Sini, S.; Jayamurthy, P.; Suresh, C.H.; Praveen, V.K.; Manoj, N.; Babu, B.P.
Development of small-molecule-based multi-luminescent fluorophores utilizing simple synthetic methodologies, as well as easily available starting materials, has gained much attention in recent years. Herein, we disclose an efficient protocol for the synthesis of N-protected 1H-indazole derivatives with diverse substituents at their 3- and 5-positions via palladium-catalyzed reactions of hydrazones and p-benzoquinones. The obtained 1H-indazole derivatives can be easily modified into donor-acceptor (D?A)-type chromophores (Indazo-Fluors) with tunable emission properties in both solid and solution state. Owing to the extent of intramolecular charge transfer, Indazo-Fluors exhibit positive solvatochromic emission spanning from blue-green to orange-red. Theoretical studies were undertaken to rationalize the observed trends in the optical properties of Indazo-Fluors. Finally, a triethylene glycol (TEG) appended Indazo-Fluor exhibiting a large Stokes shift and low cytotoxicity allowed us to use it for cell imaging. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Metal-Free Synthesis of Pyrazoles and Chromenopyrazoles from Hydrazones and Acetylenic Esters
(Wiley-Blackwell info@wiley.com, 2020) Bhaskaran, R.P.; Janardhanan, J.C.; Babu, B.P.
An efficient, metal-free synthesis of pyrazoles and chromenopyrazoles from aldehyde hydrazones and acetylenic esters has been developed. A library of molecules with diverse functional groups has been synthesized using substituted hydrazones and alkynes, both symmetrical and unsymmetrical ones. The derivatives were isolated in moderate to good yields. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Synthesis of hybrid polycycles containing fused hydroxy benzofuran and 1H-indazoles via a domino cyclization reaction
(2019) Janardhanan, J.C.; James, K.; Puthuvakkal, A.; Bhaskaran, R.P.; Suresh, C.H.; Praveen, V.K.; Manoj, N.; Babu, B.P.
A stoichiometry controlled domino cyclization reaction of hydrazone and p-benzoquinone to an angularly fused 3H-benzofuro[3,2-e]indazole core with an embedded oxygenated dibenzofuran framework under mild reaction conditions is disclosed. The reaction involves palladium catalyzed 5-hydroxy-1H-indazole formation followed by TFA mediated [3+2] annulation between the in situ formed 5-hydroxy-1H-indazole and p-benzoquinone. The developed method is attractive because of the concomitant formation of two heterocyclic rings with consecutive multiple bond forming events that include two C-C, one C-N and one C-O bonds. Spectroscopic and theoretical studies of the blue emissive benzofuroindazole derivatives have also been described. 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Synthesis of hybrid polycycles containing fused hydroxy benzofuran and 1H-indazoles via a domino cyclization reaction
(Royal Society of Chemistry, 2019) Janardhanan, J.C.; James, K.; Puthuvakkal, A.; Bhaskaran, R.P.; Suresh, C.H.; Praveen, V.K.; Manoj, N.; Babu, B.P.
A stoichiometry controlled domino cyclization reaction of hydrazone and p-benzoquinone to an angularly fused 3H-benzofuro[3,2-e]indazole core with an embedded oxygenated dibenzofuran framework under mild reaction conditions is disclosed. The reaction involves palladium catalyzed 5-hydroxy-1H-indazole formation followed by TFA mediated [3+2] annulation between the in situ formed 5-hydroxy-1H-indazole and p-benzoquinone. The developed method is attractive because of the concomitant formation of two heterocyclic rings with consecutive multiple bond forming events that include two C-C, one C-N and one C-O bonds. Spectroscopic and theoretical studies of the blue emissive benzofuroindazole derivatives have also been described. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Transition-Metal-Catalyzed Syntheses of Indazoles
(Wiley-VCH Verlag info@wiley-vch.de, 2020) Janardhanan, J.C.; Bhaskaran, R.P.; Praveen, V.K.; Manoj, N.; Babu, B.P.
Indazole is an important heterocyclic scaffold exhibiting a wide range of biological and pharmacological properties and plays a crucial role in drug design. In recent years, indazoles have gained attention in materials chemistry owing to their promising photophysical properties. The biomedical importance and natural rarity inspire the development of new practical syntheses of the indazole core. In this review, we are presenting a comprehensive overview of recent developments in the transition metal-catalyzed synthesis of indazole during the last decade. © 2020 Wiley-VCH GmbH