Catalytic asymmetric synthesis of tetrahydrocarbazoles

Tan, Fang; Cheng, Hong‐Gang

doi:10.1039/c9cc02486g

Cited by 43 publications

(16 citation statements)

References 67 publications

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“…Fused polycyclic indoles are common structural motifs found in a vast array of natural and biologically active molecules (Saxton, 1996;Knö lker and Reddy, 2002;Schmidt et al, 2012;Tan and Cheng, 2019), such as kopsihainanine A, isoelliptitoxin, and analgesic agents (Scheme 1A) (Madalengoitia and Macdonald, 1993;Carmosin et al, 2000;Chen et al, 2011). In this regard, the development of efficient methods for enantioselective construction of hydrocarbazole skeleton is still highly demanded (Sings et al, 2001;Lu et al, 2012;Zhou et al, 2015;Gu et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Enantioselective [4+2] Annulation to the Concise Synthesis of Chiral Dihydrocarbazoles

Wang

et al. 2020

iScience

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A highly efficient phosphine-catalyzed enantioselective [4 + 2] annulation of allenoates with 3-nitroindoles or 3-nitrobenzothiophenes has been developed. The protocol represents a unique dearomatizationaromatization process to access functionalized dihydrocarbazoles or dihydrodibenzothiophenes with high optical purity (up to 97% ee) under mild reaction conditions. The synthetic utility of the highly enantioselective [4 + 2] annulation enables a concise synthesis of analgesic agent.

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Section: Introductionmentioning

confidence: 99%

Enantioselective [4+2] Annulation to the Concise Synthesis of Chiral Dihydrocarbazoles

Wang

et al. 2020

iScience

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“…After reactivity of various indoles were mapped out, we next chose to exploit compound 1 as β,γ‐biselectrophilic synthon to leverage rapid construction of indole alkaloid‐type compounds. One‐step tailored assembly of tetrahydrocarbazoles (THCs) [19] was considered to be a good starting point. To our delight, reaction of 1 a with indole‐tethered malononitrile ( 6 a ) proceeded in highly regiospecific manner and afforded THC, 7 a in excellent yield and as single detectable diastereomer (Scheme 3 A).…”

Section: Methodsmentioning

confidence: 99%

Unprecedented Reactivity of γ‐Amino Cyclopentenone Enables Diversity‐Oriented Access to Functionalized Indoles and Indole‐Annulated Ring Structures

et al. 2021

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Observation of an unexpected, Lewis acid promoted displacement of latent reactive g-amino group on cyclopentenone presented unparalleled opportunity for enone functionalization and annulations with indole derivatives, which is developed in the current study. Herein, a vast range of C3/Nindolyl enones and indole alkaloid-like compound were accessed in excellent yields (up to 99 %) and selectivity through a one-pot operation. The mechanism most likely involves an unprecedented trait of Piancatelli-type rearrangement where influence of the gem-diaryl group appeared crucial.

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“…The carbazoles, [ 1 ] as well as their tetrahydro [ 2 ] and hexahydro congeners, [ 3 ] are an important class of heterocyclic compounds and the core structural motif of numerous indole alkaloids. [ 4 ] Furthermore, several synthetic pharmaceuticals carry this heterocycle.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Hexahydrocarbazole Derivatives by Reductive Indolization

et al. 2020

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The reductive indolization is a two‐step protocol performed in one flask: First, the acid‐mediated Fischer indolization of a cyclic ketone with phenylhydrazine forms an iminium ion which is subsequently reduced by a hydrido borate reagent to the indoline as the final product. We utilized this new strategy for the preparation of hexahydrocarbazole derivatives with a side chain in the quaternary C4a‐position. Starting materials were several N1‐ and aryl‐substituted phenylhydrazines and a cyclic ketone with propanoic ester moiety, which is the product of the conjugated addition of cyclohexanone to ethyl acrylate. Furthermore, benzannulated congeners as well as a pyrido[4,3‐b]indole derivative were accessed. The hexahydrocarbazole defines a molecular scaffold with two points of diversification. Therefore, several derivatives at N9 and at the C4a‐side chain were prepared.

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Catalytic asymmetric synthesis of tetrahydrocarbazoles

Abstract: This feature article summarises recent advances in catalytic asymmetric synthesis of THCs, with emphases on reaction type and reaction mechanism.

Cited by 43 publications

References 67 publications

Enantioselective [4+2] Annulation to the Concise Synthesis of Chiral Dihydrocarbazoles

Enantioselective [4+2] Annulation to the Concise Synthesis of Chiral Dihydrocarbazoles

Unprecedented Reactivity of γ‐Amino Cyclopentenone Enables Diversity‐Oriented Access to Functionalized Indoles and Indole‐Annulated Ring Structures

Preparation of Hexahydrocarbazole Derivatives by Reductive Indolization

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