Reaction of Indole Carboxylic Acid/Amide with Propargyl Alcohols: [4 + 3]-Annulation, Unexpected 3- to 2- Carboxylate/Amide Migration, and Decarboxylative Cyclization

Selvaraj, Karuppu; Debnath, Shubham; Swamy, K. C. Kumara

doi:10.1021/acs.orglett.9b01686

Cited by 36 publications

(15 citation statements)

References 80 publications

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“…Lately, Swamy's group developed an efficient Cu(OTf) 2 ‐catalyzed [4+3]‐annulation of indole‐2‐carboxylic acids/amides 22 with propargylic alcohols 1 to ϵ ‐lactones/ ϵ ‐lactams 23 under mild reaction conditions (Scheme 9). [17] Unexpectedly, the same products were also obtained from the cascade reaction of indole‐3‐amides with 1 a which catalyzed by p ‐TsOH. In this reaction, the key intermediate D was involved, and the following 1,2‐amide migration would generate intermediate E .…”

Section: Reactions Involving C‐nucleophiles To Capture Allenyl Carbocmentioning

confidence: 80%

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

2020

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Heterocyclic compounds are important organic compounds and have emerged as key scaffolds in numerous drugs, natural products, vitamins, biologically and pharmaceutically active compounds. Over the past few decades, the development of versatile methodologies employing propargylic alcohols as synthons for the construction of heterocyclic skeletons has attracted great attention from synthetic chemists. In this review, recent developments in the cascade cyclization of propargylic alcohols with diverse nucleophiles to construct heterocyclic compounds are summarized. According to the types of nucleophiles, these reactions can be divided into four categories: 1) Reactions involving C‐nucleophiles to capture allenyl carbocation; 2) Reactions involving O, S‐nucleophiles to capture allenyl carbocation; 3) Reactions involving N, P‐nucleophiles to capture allenyl carbocation; 4) Reactions involving halo‐nucleophiles to capture allenyl carbocation.

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Section: Reactions Involving C‐nucleophiles To Capture Allenyl Carbocmentioning

confidence: 80%

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

2020

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“…Recently, Swamy and co-workers reported a Lewis or Brønsted acid catalysed annulations of indole carboxylic acids/amides with propargylic alcohols for the synthesis of fused seven-membered lactones/ lactams. [64] In the presence of 10 mol% of Cu(OTf) 2 , a wide variety of indole-2-carboxylic acids 288 reacted with tertiary propargylic alcohols 221 in CH 2 Cl 2 at room temperature for 6 h to afford substituted indole fused ɛ-lactones 289 in good yields (Scheme 57). When indole-2-carboxamides 288' were used, reflux condition was necessary to guarantee the formation of ɛ-lactams 290.…”

Section: Tandem Intermolecular Annulations Of Indoles With Propargylimentioning

confidence: 99%

Tandem Annulations of Propargylic Alcohols to Indole Derivatives

Liu

Chen

2020

Adv Synth Catal

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Indole derivatives are important heterocycles in organic synthesis for serving as privileged building blocks for functional material and as key components in a lot of bioactive compounds. Propargylic alcohols, bearing alkynyl and hydroxyl functional groups, have emerged as promising feedstock materials for the construction of carbo-and heterocycles. Especially, in the last decade, the Lewis or Brønsted acid catalysed tandem annulations of propargylic alcohols to build structurally diverse indole derivatives have been well-investigated. In this review, we summarize two main synthetic strategies toward indole derivatives via the cascade reactions of propargylic alcohols: indole-ring formation involved tandem reactions and the direct function-alization of indole skeletons. We hope this review would help to develop new and more efficient protocols for the synthesis of indole-included N-heterocycles. Direct Functionalization of Indole Skeletons 3.1. Reactions Initiated with Prior Activation of the Alkyne Moiety 3.2. Reactions Initiated with Prior Activation of the Hydroxyl Group 4. Conclusions

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“…Swamy has recently shown that it was possible to react 1-methylindole-2-carboxylic acids or amides 5.6a with substituted propargyl alcohols 5.6b to afford -lactones and -lactams 5.6c, respectively, using Cu(OTf) 2 as the Lewis acid catalyst (Scheme 5.6). 63 The lactone products 5.6c, in the presence of BF 3 •OEt 2 , or a Brønsted acid such as p-TSA, extrude CO 2 , forming the 3,4-dihydrocyclopentaindoles 5.6d. Interestingly, the 1-methylindole-3-carboxylic acids and amides 5.6e in the reaction gave rise to the identical products 5.6c, leading the authors to propose a possible [1,2]-carboxylate or amide shift.…”

Section: Syn Thesismentioning

confidence: 99%

Recent Advances in Transition-Metal-Catalyzed (4+3)-Cycloadditions

Lam

Lautens²

2020

Synthesis

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A (4+3)-cycloaddition combines a four-atom synthon and three-atom synthon to form seven-membered rings. In the past decade, many improvements have been made to this class of cycloaddition, including excellent diastereo- and enantioselectivities, both intra- and intermolecularly. Through the strategic use of transition-metal catalysts, acids, bases, and organocatalysts, it is possible to perform the cycloaddition on a variety of substrates, generating novel seven-membered rings. With these advances, (4+3)-cycloaddition has also been applied to the synthesis of biologically relevant compounds and natural products. We exclude the cycloadditions of cyclic dienes such as furan, pyrrole, cyclohexadiene or cyclopentadiene as Chiu, Harmata, Mascareñas and others have recently published thorough reviews on that topic. We will however discuss the recent additions (2009–2020) to the literature for the (4+3)-cycloadditions involving other types of four-atom synthons.1 Introduction2 Rhodium2.1 Cyclopropanation/Cope Rearrangement2.2 C–H activation3 Gold, Silver4 Copper5 Palladium, Platinum, Iridium6 Dual-Activation7 Conclusion

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Reaction of Indole Carboxylic Acid/Amide with Propargyl Alcohols: [4 + 3]-Annulation, Unexpected 3- to 2- Carboxylate/Amide Migration, and Decarboxylative Cyclization

Cited by 36 publications

References 80 publications

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

Tandem Annulations of Propargylic Alcohols to Indole Derivatives

Recent Advances in Transition-Metal-Catalyzed (4+3)-Cycloadditions

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