1,6-Conjugated addition-mediated [4 + 1] annulation: an approach to 2,3-dihydrobenzofurans

Liu, Lina; Yuan, Zhenbo; Pan, Rui; Zeng, Yuye; Lin, Aijun; Yao, Hequan; Huang, Yue

doi:10.1039/c7qo00846e

Cited by 84 publications

(27 citation statements)

References 56 publications

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“…It has been described by others that the tert ‐butyl groups of the phenol derivatives obtained by addition of nucleophiles to QMs can be cleaved off under (Lewis) acidic conditions . We thus carried out a few (unoptimized) test reactions to see if a similar debutylation is also possible on the highly functionalized diester‐containing dihydrobenzofuranes 5 (Scheme ).…”

Section: Resultsmentioning

confidence: 52%

Enantioselective Catalytic [4+1]‐Cyclization of ortho‐Hydroxy‐para‐Quinone Methides with Allenoates

Zielke

Kováč

Winter

et al. 2019

Chemistry A European J

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The first highly asymmetric catalytic synthesis of densely functionalized dihydrobenzofurans is reported, which starts from ortho ‐hydroxy‐containing para ‐quinone methides. The reaction relies on an unprecedented formal [4+1]‐annulation of these quinone methides with allenoates in the presence of a commercially available chiral phosphine catalyst. The chiral dihydrobenzofurans were obtained as single diastereomers in yields up to 90 % and with enantiomeric ratios up to 95:5.

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Section: Resultsmentioning

confidence: 52%

Enantioselective Catalytic [4+1]‐Cyclization of ortho‐Hydroxy‐para‐Quinone Methides with Allenoates

Zielke

Kováč

Winter

et al. 2019

Chemistry A European J

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“…Apart from this early report by Tang, the use of chiral ammonium ylides for enantioselective five-membered ring forming reactions were not thoroughly investigated until more recently. [53, 56–58]…”

Section: Formal [4+1] Cyclizationsmentioning

confidence: 99%

“…Very recently, the groups of Yao and Huang then described the [4+1] addition of sulfonium and ammonium ylides to o -hydroxy- p -quinone methides 93 . [58] In this dihydrobenzofuran syntheses, achiral sulfonium ylides generally allowed for higher yields than the ammonium ylides. However, only by using a chiral ammonium ylide was target 88 accessed in reasonable enantiopurity but in significantly lower yield than obtained by the racemic protocol (Scheme 24B).…”

Section: Formal [4+1] Cyclizationsmentioning

confidence: 99%

Ammonium Ylide Mediated Cyclization Reactions

2018

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The use of readily accessible ammonium ylides for (asymmetric) transformations, especially cyclization reactions, has received considerable attention over the past two decades. A variety of highly enantioselective protocols to facilitate annulation reactions have recently been introduced as an alternative to other common methods including S-ylide-mediated strategies. It is the intention of this short review to provide an introduction to this field by highlighting the potential of ammonium ylides for (asymmetric) cyclization reactions as well as to present the limitations and challenges of these methods.

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“…In this context, one class of para ‐quinone methide (p‐QM) derivatives, namely, ortho ‐hydroxyphenyl‐substituted para ‐quinone methides, has recently attracted substantial interest from the synthetic community . This is because this class of reactants can act as oxygen‐containing four‐atom building blocks in catalytic asymmetric [4+n] cyclizations, especially [4+2] cyclizations (Scheme ), which can enantioselectively form oxygen‐containing six‐membered heterocyclic skeletons. For instance, in 2016, the Enders group designed this class of p ‐QM derivatives and utilized this type of reactant in an organocatalytic asymmetric [4+2] cyclization with electron‐poor alkenes as exemplified by isatin‐derived enolates (eq.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Asymmetric [4+2] Cyclization of para‐Quinone Methide Derivatives with 3‐Alkyl‐2‐vinylindoles

Jiang

Wang

et al. 2018

Adv Synth Catal

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A catalytic asymmetric [4 + 2] cyclization of para-quinone methide (p-QM) derivatives with 3alkyl-2-vinylindoles in the presence of a chiral phosphoric acid has been established, and this method provides chiral chroman frameworks in good yields (up to 98%) with high diastereoselectivities (up to > 95:5 dr) and excellent enantioselectivities (up to 96% ee). This reaction represents the first catalytic asymmetric [4 + 2] cyclization of p-QM derivatives with electron-rich alkenes, which will enrich the field of catalytic asymmetric reactions of p-QM derivatives. In addition, this catalytic asymmetric cyclization was successfully applied to 3-alkyl-2-vinylindoles. More importantly, this reaction will offer a useful method for the construction of enantioenriched chroman frameworks. Scheme 1. Profile of catalytic asymmetric [4 + 2] cyclizations involving p-QM derivatives. . Design of a catalytic asymmetric [4 + 2] cyclization of p-QM derivatives with 3-alkyl-2-vinylindoles.

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1,6-Conjugated addition-mediated [4 + 1] annulation: an approach to 2,3-dihydrobenzofurans

Abstract: 2,3-Dihydrobenzofurans were achieved via a 1,6-conjugated addition-mediated [4 + 1] annulation of ortho-hydroxyphenyl-substituted para-quinone methides in high yields with high diastereoselectivity.

Cited by 84 publications

References 56 publications

Enantioselective Catalytic [4+1]‐Cyclization of ortho‐Hydroxy‐para‐Quinone Methides with Allenoates

Enantioselective Catalytic [4+1]‐Cyclization of ortho‐Hydroxy‐para‐Quinone Methides with Allenoates

Ammonium Ylide Mediated Cyclization Reactions

Catalytic Asymmetric [4+2] Cyclization of para‐Quinone Methide Derivatives with 3‐Alkyl‐2‐vinylindoles

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