Lewis Acid-Catalyzed [3+3] Annulation of Donor–Acceptor Cyclopropanes and Indonyl Alcohols: One Step Synthesis of Substituted Carbazoles with Promising Photophysical Properties

Varshnaya, Rohit Kumar; Banerjee, Prabal

doi:10.1021/acs.joc.8b02733

Cited by 35 publications

(14 citation statements)

References 76 publications

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“…Diastereomer 6a has the ketone carbonyl in close proximity with the basic nitrogen that allows 1,2-migration with concurrent C–C bond formation with the ketone carbonyl carbon followed by N to O Lewis acid/proton exchange and subsequent loss of water. If the alternative ring cleavage/readdition pathway had occurred, the % ee of 8a would have been the average of the % ee values of 5a and 6a .…”

Section: Resultsmentioning

confidence: 99%

Stereoretentive Catalytic [3+2]-Cycloaddition/Rearrangement/Decarboxylation Reactions of Indoles with Non-Racemic Donor–Acceptor Cyclopropanes

et al. 2023

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A highly enantioselective synthesis of chiral dihydro-3H-carbazole-2-carboxylate derivatives is reported via a “one-pot” cyclopentannulation-rearrangement cascade reaction that is sequentially catalyzed by nickel(II) perchlorate hexahydrate and scandium(III) trifluoromethanesulfonate with 3-methylindole and non-racemic donor–acceptor cyclopropanes in high yields and enantioretention under mild reaction conditions. Highly diastereoselective [3+2]-cycloaddition is dependent on 3-methylindole substituents. In addition, a further transformation of these dihydro-3H-carbazole-2-carboxylates via hydrolysis and decarboxylation under unexpectedly mild reaction conditions provides straightforward access to the decarboxylated compounds in moderate yields with high retention of enantiomeric purity.

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Section: Resultsmentioning

confidence: 99%

Stereoretentive Catalytic [3+2]-Cycloaddition/Rearrangement/Decarboxylation Reactions of Indoles with Non-Racemic Donor–Acceptor Cyclopropanes

et al. 2023

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“…Initially, methylation of the hydroxy group of the β-naphthol derivative 3aa was achieved by reacting with one equivalent of methyl iodide, taking K 2 CO 3 as a base . Later, the Krapcho decarboxylation was also performed and successfully obtained the desired monodecarboxylated product in moderate yield …”

Section: Resultsmentioning

confidence: 99%

Merging Two Strained Carbocycles: Lewis Acid Catalyzed Remote Site-Selective Friedel–Crafts Alkylation of in Situ Generated β-Naphthol

2022

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Lewis acid catalyzed tandem activation of the two smallest carbocycles, 3-ethoxy cyclobutanones, and donor–acceptor cyclopropanes has been demonstrated. The diphenyl-substituted 3-ethoxy cyclobutanone rearranges itself by intramolecular cyclization for the in situ generation of 1-phenyl 2-naphthol, which further undergoes remote site-selective Friedel–Crafts alkylation with donor–acceptor cyclopropane to synthesize a series of γ-naphthyl butyric acid derivatives. Further control experiments for mechanistic investigations and synthetic applications have also been carried out.

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“…Recently, our group has also documented a protocol for the in‐situ generation of isocyanates [23] . Our ongoing interest in the electroorganic synthesis and affirmative experiences in DACs [5b,7b,8a,24] prompted us towards electrochemical activation of DACs. In this context, Shono et al .…”

Section: Methodsmentioning

confidence: 99%

Electricity Driven 1,3‐Oxohydroxylation of Donor‐Acceptor Cyclopropanes: a Mild and Straightforward Access to β‐Hydroxy Ketones

2021

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An unprecedented external oxidant-free electrochemical protocol for 1, 3-oxohydroxylation of donor-acceptor cyclopropane is disclosed. The strategy encompasses the activation of the labile π-electron cloud of the aryl ring to cleave the strained C sp 3 À C sp 3 bond of cyclopropane to afford the β-hydroxy ketones via insertion of molecular oxygen. More significantly, based on the detailed mechanistic investigations and cyclic voltammetry experiments, a plausible mechanism is proposed.The magnificent journey of the most strained carbocycle named cyclopropane began long back in the 1970s. [1] The fundamentals laid by the frontiers have enabled the scientific community to exploit them for the construction of several complex molecular architectures cleverly. Bearing the ring strain of 115 KJ mol À 1 with an inefficient orbital overlap induces a significant amount of π-character in the bent CÀ C bonds of Cylclopropanes. [2] Further, the introduction of the donor and acceptor groups at the vicinal position of these CÀ C bonds induces a push-pull effect which polarizes the cycloalkane. [3] The previous decade has encountered a huge renaissance in the area of donor-acceptor cyclopropanes (DACs). [4] However, most of these documented protocols rely on the concept of Lewis [5] or Bronsted acid [6] catalysis, which cleaves the CÀ C bond in a heterolytic fashion and renders a zwitterionic species. [4] These 1,3-dipole species have been utilized for several cycloadditions, [7] rearrangements, [8] and ring-opening reactions. [9] Among them, 1,3-bifunctionalization of these DACs are still rare and relatively underexplored. However, there are several reports which demonstrate that these 1,3-dipoles can be seized with amines, [10a] azides, [10b] phenols, [10c] thiols [10d] etc. wherein, the ensuing anion traps the proton. In 2011, Sparr and Gilmour manifested the enantioselective 1,3-dichlorination of cyclopropane carbaldehyde in an organocatalytic fashion. [11] Later, in 2014, Werz and coworkers disclosed the ring-opening 1,3-dichlorination in the presence of iodobenzene dichloride (Scheme 1a). [12a] Followed by this, in 2017, the same group documented the reactivity of DACs with chalcogenyl chloride and bromides (Scheme 1b). [12b-c] In continuation to the endeav-[a

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Lewis Acid-Catalyzed [3+3] Annulation of Donor–Acceptor Cyclopropanes and Indonyl Alcohols: One Step Synthesis of Substituted Carbazoles with Promising Photophysical Properties

Cited by 35 publications

References 76 publications

Stereoretentive Catalytic [3+2]-Cycloaddition/Rearrangement/Decarboxylation Reactions of Indoles with Non-Racemic Donor–Acceptor Cyclopropanes

Stereoretentive Catalytic [3+2]-Cycloaddition/Rearrangement/Decarboxylation Reactions of Indoles with Non-Racemic Donor–Acceptor Cyclopropanes

Merging Two Strained Carbocycles: Lewis Acid Catalyzed Remote Site-Selective Friedel–Crafts Alkylation of in Situ Generated β-Naphthol

Electricity Driven 1,3‐Oxohydroxylation of Donor‐Acceptor Cyclopropanes: a Mild and Straightforward Access to β‐Hydroxy Ketones

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