Scope and advances in the catalytic propargylic substitution reaction

Roy, Rashmi; Saha, Satyajit

doi:10.1039/c8ra04481c

Cited by 93 publications

(32 citation statements)

References 259 publications

(438 reference statements)

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“…The chiral N-alkylated products could be efficiently functionalized further, providing new classes of valuable heterocycles. Propargylic compounds are important building blocks in synthetic chemistry because they can be transformed into a wide range of organic derivatives, including heterocycles [62,63]. Shao and coworkers investigated the enantioselective N-propargylation of indoles and carbazoles (Scheme 33) [64].…”

Section: Other Direct Methodsmentioning

confidence: 99%

Enantioselective Catalytic Synthesis of N-alkylated Indoles

Trubitsõn

Kanger

2020

Symmetry

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During the past two decades, the interest in new methodologies for the synthesis of chiral N-functionalized indoles has grown rapidly. The review illustrates efficient applications of organocatalytic and organometallic strategies for the construction of chiral α-N-branched indoles. Both the direct functionalization of the indole core and indirect methods based on asymmetric N-alkylation of indolines, isatins and 4,7-dihydroindoles are discussed.

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Section: Other Direct Methodsmentioning

confidence: 99%

Enantioselective Catalytic Synthesis of N-alkylated Indoles

Trubitsõn

Kanger

2020

Symmetry

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“…The corresponding allenyl–indolines 5 were delivered in good yields (40–94 %) and diastereoisomeric ratio up to 80:20 (Scheme ). It is worth mentioning that this approach represents the first example of indole dearomatization with concomitant site‐selective installation of bi‐, tri‐, and tetra‐substituted allenyl units …”

Section: Figurementioning

confidence: 99%

Allylic and Allenylic Dearomatization of Indoles Promoted by Graphene Oxide by Covalent Grafting Activation Mode

Lombardi

Bellini

Bottoni

et al. 2020

Chemistry A European J

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The site‐selective allylative and allenylative dearomatization of indoles with alcohols was performed under carbocatalytic regime in the presence of graphene oxide (GO, 10 wt % loading) as the promoter. Metal‐free conditions, absence of stoichiometric additive, environmentally friendly conditions (H2O/CH3CN, 55 °C, 6 h), broad substrate scope (33 examples, yield up to 92 %) and excellent site‐ and stereoselectivity characterize the present methodology. Moreover, a covalent activation model exerted by GO functionalities was corroborated by spectroscopic, experimental and computational evidences. Recovering and regeneration of the GO catalyst through simple acidic treatment was also documented.

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“…Intramolecular cyclization reactions involving propargylic alcohols have been investigated as well . The hydroxyl group can be replaced in nucleophilic substitution reactions by a variety of nucleophiles (Scheme a) . Tandem reactions constituting of a propargylic nucleophilic substitution reaction followed by a cyclization can afford a variety of cyclic and heterocyclic ring systems .…”

Section: Introductionmentioning

confidence: 99%

“…Suppression of rearrangement side reactions such as the Meyer‐Schuster rearrangement[16c] or others can also be a challenge. As such, the search for catalyst systems that perform the reaction at reasonably low temperatures and with a high level of selectivity is still ongoing, as demonstrated by the number of publications and review articles on the topic that have appeared in the last few years …”

Section: Introductionmentioning

confidence: 99%

Ferrocenium Cations as Catalysts for the Etherification of Cyclopropyl‐Substituted Propargylic Alcohols: Ene‐yne Formation and Mechanistic Insights

et al. 2019

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Commercial ferrocenium hexafluorophosphate ([FeCp 2 ]PF 6 ) and ferrocenium boronic acid hexafluoroantimonate ([FcB(OH) 2 ]SbF 6 ) were found to be efficient catalysts for the etherification of terminal, tertiary, cyclopropyl-substituted propargylic alcohols through nucleophilic substitution with primary and secondary alcohols. The alcohol nucleophiles and the propargylic alcohols were employed in a nearly equimolar amount and no further additives were required. After 2 h reaction time at 40°C in CH 2 Cl 2 and 3 to 5 mol-% catalyst load, aromatic, cyclopropyl-substituted propargylic alcohols gave rearranged, conjugated ene-yne products as single isomers in 35 to 73 % isolated yields. Cyclopropyl-substituted propargylic alcohols [a] 7349 Accordingly, we decided to synthesize cyclopropyl-substituted propargylic alcohol substrates (4 in Scheme 1c) to investigate whether the reaction proceeds through a radical mechanism. Cyclopropyl-substituted radicals 6 (Scheme 1c) may ringopen to form alkenes, but carbocation 5 may also have this tendency (vide infra). As exemplified in Scheme 1c, ene-ynes 7 can form through rearrangement if a cyclopropyl-substituted propargylic alcohol 4 is employed. [35] The employment of cyclopropyl-substituted propargylic alcohols in reactions with alcohols to give conjugated, achiral enynes has been reported previously only four times, utilizing Yb(OTf ) 3 , [36a] triflic acid (TfOH), [36b] HAuCl 4[36c] and ruthenium complexes [36d] as catalysts. In these reports, the nucleophile was either the solvent [36b,36c] or employed in large excess. [36a,36d] Herein, we report ferrocenium-catalyzed substitution reactions with these substrates and isolated both ene-yne products and cyclopropylsubstituted products, depending on the substituent R in 4. Experimental evidence points toward an ionic mechanism through carbocation 5 (Scheme 1c). [37] Eur.Scheme 2. Formation of the cyclopropyl-substituted intermediate 21 and ring-opening.

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Scope and advances in the catalytic propargylic substitution reaction

Abstract: Direct nucleophilic displacement of the alpha-hydroxy of the propargylic alcohol is one of the sought-after methods in the current scenario. An updated summary of the recent developments in this field is presented here.

Cited by 93 publications

References 259 publications

Enantioselective Catalytic Synthesis of N-alkylated Indoles

Enantioselective Catalytic Synthesis of N-alkylated Indoles

Allylic and Allenylic Dearomatization of Indoles Promoted by Graphene Oxide by Covalent Grafting Activation Mode

Ferrocenium Cations as Catalysts for the Etherification of Cyclopropyl‐Substituted Propargylic Alcohols: Ene‐yne Formation and Mechanistic Insights

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