@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 {49688, title = {Conjugate addition/cyclization of propanal with isatylidene malononitriles: an efficient one-pot organocatalytic approach for the synthesis of 3'-methyl spiro[2H-pyran-3,4'-indoline]}, journal = {Organic \& Biomolecular Chemistry}, volume = {23}, year = {2025}, month = {JUN}, pages = {6214-6219}, type = {Article}, abstract = {

The organocatalyzed one-pot Michael addition reaction of propanal to isatylidene malononitriles remains largely unexplored due to challenges in controlling the reaction and preventing side processes such as aldol condensation, self-aldolization, and 1,3-dipolar cycloaddition. In this study, we introduce a one-pot methodology for the synthesis of 3 {\textquoteleft}-alkyl spiro[2H-pyran-3,4 {\textquoteleft}-indoline] via an organocatalyzed Michael addition of simple propanal to isatylidene malononitrile derivatives, which are generated in situ from isatin derivatives and malononitrile. Subsequent reduction of the Michael adduct with NaBH4 leads to the target product with high efficiency under mild conditions. This strategy offers several advantages, including environmental sustainability, high to excellent yields, shorter reaction times, cost-effectiveness, and ease of implementation.

}, issn = {1477-0520}, doi = {10.1039/d5ob00553a}, author = {Patil, Baliram R. and Nichinde, Chandrakant B. and Girase, Amardipsing S. and Chaudhari, Suryakant S. and Kinage, Anil K.} } @article {49505, title = {Efficient synthesis of 3,3'-Spirooxindole γ-Butyrolactone via Rongalite-mediated domino reductive aldol and spiro-lactonization reactions}, journal = {ChemistrySelect}, volume = {10}, year = {2025}, month = {FEB}, pages = {e202405996}, type = {Article}, abstract = {

In this study, we develop a novel methodology involving rongalite-mediated domino reductive/aldol reaction, followed by spiro-lactonization of 2-oxoindolin-3-ylidene acetates/malonates in presence of base to synthesis of 3,3 {\textquoteleft}-spirooxindole gamma-butyrolactone. The detail study, such as effect of solvent, effect of different base and substrate has been carried out. Scale up of this methodology is also done. Sodium hydroxymethanesulfinate dihydrate (rongalite) concurrently has a dual role in this context; it acts as a reducing agent as well as C1 synthon. This approach offers several advantages, such as being metal- and catalyst-free, involving a simple reaction protocol, having a wide substrate scope, using water as a green solvent, and providing good to excellent yields of the products under mild reaction conditions.

}, keywords = {(+/-) Coixspirolactam A \& [3, 3 {\textquoteleft}-spirooxindole gamma-butyrolactone], Domino reductive/aldol/spiro-lactonization, Good step economy, Rongalite as reductant \& C1 synthon, Water as a green solvent}, issn = {2365-6549}, doi = {10.1002/slct.202405996}, author = {Chaudhari, Suryakant S. and Nichinde, Chandrakant B. and Patil, Baliram R. and Girase, Amardipsing S. and Kinage, Anil K.} } @article {49889, title = {Rongalite-promoted self-dimerization of 3-acylidene-2-oxindoles: a diastereoselective route to synthesis of bispirooxindoles}, journal = {Organic \& Biomolecular Chemistry}, volume = {23}, year = {2025}, month = {OCT}, pages = {8687-8694}, type = {Article}, abstract = {

A facile and efficient one-pot rongalite-mediated self-dimerization of 3-acylidene-2-oxindoles has been developed for the diastereoselective synthesis of highly functionalized dispirocyclopentanebisoxindoles. The reaction proceeds via a domino sequence involving intermolecular Michael addition followed by intramolecular aldol cyclization under basic conditions. Rongalite, an inexpensive and readily available reagent (similar to\$0.03 per g), plays a crucial role in promoting the transformation, offering significant advantages such as operational simplicity, step economy, scalability to gram-scale synthesis, and potential for post-functionalization. This methodology provides an efficient route to structurally complex oxindole frameworks with high stereocontrol, demonstrating broad synthetic utility.

}, issn = {1477-0520}, doi = {10.1039/d5ob01069a}, author = {Chaudhari, Suryakant S. and Nichinde, Chandrakant B. and Patil, Baliram R. and Girase, Amardipsing S. and Kaulage, Sandeep H. and Kinage, Anil K.} } @article {49536, title = {Sequential nitro-michael addition and reductive cyclization cascade reaction for diastereoselective synthesis of multifunctionalized 3,3'-pyrrolidinyl-spirooxindoles}, journal = {European Journal of Organic Chemistry}, volume = {28}, year = {2025}, month = {FEB}, type = {Article}, abstract = {

In this investigation, we elucidated, one-pot two stage efficient synthesis of multifuctionalized spiro[oxindole -3,3 {\textquoteleft}-pyrrolidine]. The methodology proceeds via organocatalyzed nitro-Michael addition reaction between indolylidenecyanoesters and nitroalkanes to formed nitro-Michael adduct which transformed into multifunctionalized 3,3 {\textquoteleft}-pyrrolidinyl-spirooxindoles by metal catalyzed reductive cyclization cascade. DFT investigations were conducted to elucidate the mechanism underlying the preferential reduction of the nitro group, with subsequent attack on the nitrile and ester groups remain inert throughout the reaction process. The approach is operationally simple, easily scalable, exhibits compatibility with readily accessible starting material and catalysts, thereby emphasizing cost-effectiveness.

}, keywords = {3 {\textquoteleft}-pyrrolidinyl spirooxindoles, DFT study for regioselective cyclization, Diastereoselective 3, organocatalysis, Pd/C catalysed partial reductive spirocyclization}, issn = {1434-193X}, doi = {10.1002/ejoc.202401121}, author = {Nichinde, Chandrakant B. and Bhati, Meema and Girase, Amardipsing S. and Patil, Baliram R. and Chaudhari, Suryakant S. and Gamidi, Rama Krishna and Joshi, Kavita and Kinage, Anil K.} } @article {50028, title = {Thiophenol-mediated metal-free chemoselective conjugate reduction strategy for 3-alkylidene oxindoles}, journal = {RSC Advances }, volume = {16}, year = {2026}, month = {FEB }, pages = {7702-7706}, type = {Article}, abstract = {

A mild and metal-free thiophenol-mediated chemoselective conjugate reduction of 3-alkylidene oxindoles via a thiol-ene-type Michael addition was effectively carried out. Thiophenol as an efficient reductant is used in DMSO, and the transformation proceeds without the need for metal catalyst, external hydrogen source, or harsh reagents. The reaction displays a broad substrate scope, accommodating both electron-donating and electron-withdrawing substituents, and delivers 3-alkyloxindoles in high yields with excellent beta-selectivity. This sustainable and operationally simple method unveils a distinct thiol-mediated reduction mechanism, providing a green and versatile approach for accessing reduced oxindole derivatives and related Michael acceptors.

}, doi = {10.1039/d5ra09175f}, author = {Patil, Baliram R. and Nichinde, Chandrakant B. and Girase, Amardipsing S. and Chaudhari, Suryakant S. and Kinage, Anil K.} }