Catalytic Asymmetric Assembly of C3-Monosubstituted Chiral Carbazolones and Concise Formal Synthesis of (−)-Aspidofractinine: Application of Enantioselective Pd-Catalyzed Decarboxylative Protonation of Carbazolones

Zhao, Ruirui; Sun, Zhong‐Wen; Mo, Mingjie; Peng, Fangzhi; Shao, Zhihui

doi:10.1021/ol501877x

Cited by 34 publications

(16 citation statements)

References 33 publications

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“…Communications example,palladium complexes [22] or enzymes. [10a, 23] Unlike the former examples,a sw ell as decarboxylative addition reactions, [10c,d,24] the DW reaction described herein is particularly challenging as it presupposes the stereoselective transfer of the smallest electrophile,aproton, in the presence of significant amounts of acid in ac omplex multistep reaction (Scheme 2).…”

Section: Angewandte Chemiementioning

confidence: 99%

The Enantioselective Dakin–West Reaction

et al. 2016

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Here we report the development of the first enantioselective Dakin-West reaction, yielding a-acetamido methylketones with up to 58 %eewith good yields.T wo of the obtained products were recrystallized once to achieve up to 84 %ee. The employed methylimidazole-containing oligopeptides catalyze both the acetylation of the azlactone intermediate and the terminal enantioselective decarboxylative protonation. We propose ad ispersion-controlled reaction path that determines the asymmetric reprotonation of the intermediate enolate after the decarboxylation.Even though the Dakin-West (DW) reaction dates back to 1928, [1] it is still one of the most effective synthetic procedures to prepare a-acylamido ketones from primary a-amino acids. [2] Generally,t he treatment of an amino acid with an acid anhydride and base,t ypically pyridine,a te levated temperature provides the desired product upon liberation of CO 2 (Scheme 1). Numerous modifications of the original reaction conditions were developed, [2] including catalytic variants, [3] broadening its scope and applicability.U nsurprisingly,the DW reaction found application in the preparation of a-acylamido ketones as valuable precursors for various biologically active compounds, [4] and even in Woodwards fundamental total synthesis of strychnine. [5] Remarkably,n o asymmetric variant has been developed to date,thus restricting the use of this important reaction in modern synthetic chemistry.

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Section: Angewandte Chemiementioning

confidence: 99%

The Enantioselective Dakin–West Reaction

et al. 2016

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“…In 2014, Peng, Shao and co‐workers reported the enantioselective synthesis of C‐3 monosubstituted carbazolones via the DAP of allyl β‐keto esters (±)‐ 12 . Procedures S F and S M (Table ) did not mediate the decarboxylative protonation of (±)‐ 12a .…”

Section: Ketonesmentioning

confidence: 99%

Palladium/Unichiral Ligand‐Catalyzed Decarboxylative Asymmetric Protonation of Racemic β‐Oxoallyl Esters

Мuzart

2019

Adv Synth Catal

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Scheme 9. DAPs leading to a-arylisoflavanones (R 1 ,R 2 ,R 3 ,R 4 = H, Me,OMe;R 2 -R 3 = CH 2 OCH 2 ).Scheme 10. DAPs leading to 7-(naphthalen-2-ylmethoxy)isoflavanones (R 1 ,R 2 ,R 3 ,R 4 = H, OMe,R 1 -R 2 = CHCH=CHCH). Scheme11. DAPs leading to a-aryloxindoles (R 1 ,R 2 ,R 3 , R 4 = H, Me,OMe;R 2 -R 3 = CH 2 OCH 2 ). Scheme 21. Guirysmechanistic proposal for the palladium-catalyzed DPAofa llyl b-keto esters with formic acid. Scheme 22. Plausible enantiodetermining transition state for the Meldrumsa cid-mediated DAPof( AE)-18a. Scheme 23. Alternative plausible enantiodetermining transition state for the Meldrumsacid-mediated DAPof( AE)-18a. Scheme 24. Plausible enantiodetermining transition state for the Meldrumsa cid-mediated DAPof( AE)-2a. Scheme 25. Plausible enantiodetermining transition state for the Meldrumsa cid-mediated DAPof( AE)-7a. Scheme 26. Plausible enantiodetermining transition states for the formic acid-mediated DAPof(AE)-7a. Scheme 27. Plausible enantiodetermining transition states for the formic acid-mediated DAPs of (AE)-2a and (AE)-7a.

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“…[95] Shao, Peng and co-workers have also applied this strategy in natural product synthesis, to form similar pentacyclic frameworks 148 and 150 in good yields. [96,97] Finally Weinreb and co-workersr eported the cyclopropanation spirocyclisation of 151,w hich upon treatment with either AgOTf or AgBF 4 ,a fforded the spirocyclic indolenine 152 in excellent yield. [98] Intramolecular Mitsunobu reactions have also been shown to be effective for spirocyclic indolenine synthesis (Scheme22).…”

Section: Alkylationsmentioning

confidence: 99%

“…Banwell and co‐workers also used a AgOTf promoted alkylation of 145 in their total synthesis of (±)‐limaspermidine and (±)‐1‐acetylaspidoalbidine precursor 146 . Shao, Peng and co‐workers have also applied this strategy in natural product synthesis, to form similar pentacyclic frameworks 148 and 150 in good yields . Finally Weinreb and co‐workers reported the cyclopropanation spirocyclisation of 151 , which upon treatment with either AgOTf or AgBF 4 , afforded the spirocyclic indolenine 152 in excellent yield …”

Section: Indole Dearomatisationsmentioning

confidence: 99%

Synthesis of Spirocyclic Indolenines

James

O’Brien

Taylor

et al. 2015

Chemistry A European J

299

119

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This Review provides an in-depth account of the synthesis of spirocyclic indolenines. Over the last 77 years, a wide array of diverse synthetic methods has been developed in order to generate these synthetically useful and biologically important spirocyclic scaffolds. The main synthetic strategies discussed are grouped into three main categories, namely interrupted Fischer indolisations, dearomatisation reactions of indoles and condensation reactions. The historical background, common synthetic challenges, current state-of-the-art and future perspectives of this field are examined.

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Catalytic Asymmetric Assembly of C3-Monosubstituted Chiral Carbazolones and Concise Formal Synthesis of (−)-Aspidofractinine: Application of Enantioselective Pd-Catalyzed Decarboxylative Protonation of Carbazolones

Cited by 34 publications

References 33 publications

The Enantioselective Dakin–West Reaction

The Enantioselective Dakin–West Reaction

Palladium/Unichiral Ligand‐Catalyzed Decarboxylative Asymmetric Protonation of Racemic β‐Oxoallyl Esters

Synthesis of Spirocyclic Indolenines

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