Construction of highly functionalized carbazoles via condensation of an enolate to a nitro group

Poudel, Tej Narayan; Lee, Yong Rok

doi:10.1039/c5sc02407b

Cited by 73 publications

(23 citation statements)

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“…A simple, unique, and efficient Cs 2 CO 3 ‐mediated tandem annulation reaction of 2‐nitrocinnamaldehydes 8 or 2‐nitrochalcones 9 with β‐ketoesters 10 for the construction of 3‐hydroxy carbazole esters 11 was demonstrated by our group (Scheme a) . Many of the previously reported syntheses of carbazoles require either highly elaborate biaryls or biarylamines to build the central pyrrole ring, or prefunctionalized indole derivatives for the benzannulation reaction.…”

Section: Cs2co3‐mediated Benzannulation Reactionsmentioning

confidence: 95%

Recent Progress in Transition‐Metal‐Free, Base‐Mediated Benzannulation Reactions for the Synthesis of a Diverse Range of Aromatic and Heteroaromatic Compounds

et al. 2018

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Benzene and itsderivativesare the most abundant substructures of several interesting classes of compound, such as bioactive molecules. Owing to their importance, the development of methods for their constructionh as attracted considerable attention.H owever,t he regioselectives ynthesis of polysubstituted aromatic and heteroaromatic compounds by using aromatic substitution is challenging, because it provides derivatives with restricted substitution patterns. Therefore, the benzannulation reaction-the assembly of benzene derivatives from acyclicp recursors-constitutes as uperior and highly versatile approach to polysubstituted aromatic and heteroaromatic compounds,a nd variouse fficient benzannulation reactions have been reported.R epresentative examples include Cs 2 CO 3 , t-BuOK,a nd DBU-catalyzed reactions for the construction of valuableb enzene derivatives. The central objective of this Focus Review is to highlight base-mediated benzannulation reactions under transitionmetal-free conditions for the construction of aromatic and heteroaromatic compounds.[a] Dr.Recently,P an and co-workers investigated the K 2 CO 3 -catalyzed cascade benzannulation reaction of b-keto sulfones 1 with acetylene ketones 2 by using 30 %m ol K 2 CO 3 without other additives,w hich afforded new sulfonylbenzene derivatives 3 in good yields through ab enzannulation reaction (Scheme 1a). [18] Av ariety of electron-donating ande lectron-withdrawing groups were well-tolerated under the optimized reaction conditions. The proposed reactionpathway proceeded through se-quentialM ichael addition, intramolecular cyclization, hydrogen abstraction, and dehydration reactions (Scheme 1b).Scheme55. Synthesis of unsymmetrical biaryls from the annulation/aromatizationr eactionsof1 ,4-pentanedienes with nitroalkanes.Scheme56. DBU-promoted [5+ +1] annulation reaction of a-alkenoyl ketene-S,S-acetalswith nitroalkanes.

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Section: Cs2co3‐mediated Benzannulation Reactionsmentioning

confidence: 95%

Recent Progress in Transition‐Metal‐Free, Base‐Mediated Benzannulation Reactions for the Synthesis of a Diverse Range of Aromatic and Heteroaromatic Compounds

et al. 2018

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“…A transition metal free and mild base promoted condensation of 2-nitrocinnamaldehydes or 2-nitrochalcones 24 with β-ketoesters 25 afforded carbazole derivatives 26 (Scheme 6). [15] This transformation presumably involves an intramolecular addition of enolate 27 to nitro group and a unique in-situ cleavage of NÀ O bond (28) under nonreductive conditions.…”

Section: [3 + 3] Benzannulation Reactionsmentioning

confidence: 99%

Benzannulation Reactions: A Case for Perspective Change From Arene Decoration to Arene Construction

Swami

Yadav

Menon

2021

The Chemical Record

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“…In particular, a readily available aldo‐nitro compound, 2‐nitrocinnamaldehyde, has often been used in the synthesis of heterocycles. For example, Poudel and Lee described the synthesis of highly functionalized carbazole 161 under transition‐metal‐free conditions by using nitrocinnamaldehyde and β‐ketoester as substrates and a mild base as the catalyst (Scheme ) . The mechanism of the reaction involves 1) intermolecular conjugate addition of an enolate to the enal bearing an o‐ nitro group; and 2) in situ N–O bond cleavage under the non‐reductive conditions, which couples with an intramolecular aldo and dehydration reaction sequence, leading to the formation of 161 .…”

Section: Benzaldo‐x Bifunctional Building Blocks and Their Heterocyclmentioning

confidence: 99%

Aldo‐X Bifunctional Building Blocks for the Synthesis of Heterocycles

Ravichandiran

Lai

2016

The Chemical Record

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Compounds containing oxygen, nitrogen, or sulfur atoms inside the rings are attracting much attention and interest due to their biological importance. In recent years, several methods for the synthesis of such molecules have been reported by using aldo-X bifunctional building blocks (AXB3 s) as substrates; these are a wide class of organic molecules that contain at least two reactive sites, among them, one aldehyde, acetal, or semiacetal group was involved. Because of the multiple reactivities, AXB3 s are widely used in the one-pot synthesis of biologically important heterocycles. This review summarizes the synthesis of important heterocycles by using AXB3 s as pivotal components in establishing multicomponent reactions, tandem reactions, and so forth. In many cases, the established reaction systems with AXB3 s were characterized by some green properties, such as easy access to the substrate, mild and environmentally benign conditions, and wide scope of the substrate.

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Construction of highly functionalized carbazoles via condensation of an enolate to a nitro group

Abstract: A transition-metal-free unique tandem annulation reaction has been developed for the synthesis of various functionalized 3-hydroxycarbazoles.

Cited by 73 publications

References 73 publications

Recent Progress in Transition‐Metal‐Free, Base‐Mediated Benzannulation Reactions for the Synthesis of a Diverse Range of Aromatic and Heteroaromatic Compounds

Recent Progress in Transition‐Metal‐Free, Base‐Mediated Benzannulation Reactions for the Synthesis of a Diverse Range of Aromatic and Heteroaromatic Compounds

Benzannulation Reactions: A Case for Perspective Change From Arene Decoration to Arene Construction

Aldo‐X Bifunctional Building Blocks for the Synthesis of Heterocycles

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