Microwave-Assisted One-Pot Synthesisof 2,4-Disubstituted Quinolines under Solvent-Free Conditions

Yadav, J. S.; Reddy, B. V. Subba; Rao, R. Srinivasa; Naveenkumar, V.; Nagaiah, K.

doi:10.1055/s-2003-40531

Cited by 33 publications

(9 citation statements)

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“…As mentioned above, our synthetic scheme has been demonstrated on a terminal alkyne. Previous methods for the preparation of quinolines are generally restricted to this type of substrates, although distinct mechanistic hypotheses have been proposed (e.g., initial attack of imine carbon by alkyne, direct Diels–Alder reaction). , Gratifyingly, the versatility of our silver-based system is manifested by the broad terminal alkyne substrate scope, with the formation of desired quinoline derivatives regardless of electron-donating or -withdrawing character of the functionality on aniline (Table , 4m-4w ). Also noteworthy is the achievement of a relatively high yield for an aliphatic terminal alkyne ( 4x ), in marked contrast with the reactivity pattern for aliphatic internal alkynes.…”

Section: Resultsmentioning

confidence: 99%

Silver-Mediated C–H Activation: Oxidative Coupling/Cyclization of N-Arylimines and Alkynes for the Synthesis of Quinolines

et al. 2011

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A silver-mediated tandem protocol for the synthesis of quinolines involving the oxidative coupling/cyclization of N-arylimines and alkynes has been developed. We demonstrated that scenario-dependent metalation could occur either at the ortho C-H bond of an N-arylimine through protonation-driven enhancement of acidity or at the terminal C-H bond of an alkyne by virtue of the carbophilic π-acidity of silver. The diverse set of mechanistic manifolds implemented with a single type of experimental protocol points toward the importance of stringent reactivity analysis of each individual potentially reactive molecular site. Importantly, the direct arene C-H bond activation provides a unique and distinct mechanistic handle for the expansion of reactivity paradigms for silver. As expected, the protocol allows for the incorporation of both internal and terminal alkynes into the products, and in addition, both electron-withdrawing and -donating groups are tolerated on N-arylimines, thus enabling the vast expansion of substituent architectures on quinoline framework. Further, an intriguing phenomenon of structural isomerization and chemical bond cleavage has been observed for aliphatic internal alkynes.

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Section: Resultsmentioning

confidence: 99%

Silver-Mediated C–H Activation: Oxidative Coupling/Cyclization of N-Arylimines and Alkynes for the Synthesis of Quinolines

et al. 2011

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“…A concise three-component synthesis of 2,4-disubstituted quinolines was reported by Yadav and co-workers. 54 A microwave assisted reaction of anilines 97, aldehydes 98, and alkynes 99 that is catalyzed by montmorillonite clay doped with copper(I) bromide the quinoline derivatives 100 are obtained with 3-5 min in good to excellent yields (Scheme 44). Presumably, the sequence is initiated by an amino alkylation of the terminal alkyne followed by a cycloisomerization and an oxidative aromatization.…”

Section: Miscellaneous Processesmentioning

confidence: 99%

Multi-component syntheses of heterocycles by transition-metal catalysis

2007

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For a long time multi-component syntheses of heterocycles have undeniably been a domain of classical carbonyl condensation chemistry. However, the advent of transition-metal catalysis not only has fertilized strategies in heterocyclic synthesis by uni- and bimolecular transformations but the past decade has also witnessed a rapid development of transition-metal catalysis in new multi-component reactions (MCR). Expectedly, palladium catalyzed processes have received a dominant position, yet, other transition-metal complexes are catching up implying organometallic elementary steps that reach even further than cross-coupling and carbometallation. Besides domino MCRs that are purely based upon organometallic catalysis the sequential and consecutive combination with condensation, addition and cycloaddition steps opens a vast playground for the invention of new sequences in heterocyclic synthesis. This tutorial review outlines the underlying reaction based principles of transition-metal catalysis in multi-component syntheses of heterocycles, summarizes recent developments of palladium catalyzed MCR, and highlights the more recent contributions to MCR based heterocyclic synthesis by virtue of rhodium, ruthenium, and copper catalysis.

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“…Addition of alkynes to imines generated in situ can lead to quinolines when the reaction is conducted in the presence of copper chloride [126] or montmorillonite clay doped with copper bromide [127]. In the latter case, the reaction was performed under solvent-free conditions and was microwave assisted (Scheme 8.57).…”

Section: Synthesis Of Quinolines and Isoquinolinesmentioning

confidence: 99%