Enantioselective Synthesis of Chromenes via a Palladium‐Catalyzed Asymmetric Redox‐Relay Heck Reaction

Jiang, Zhonghao; Gao, Ang; Li, Hao; Chen, Di; Ding, Chang‐Hua; Xu, Bin; Hou, Xue‐Long

doi:10.1002/asia.201701504

Cited by 15 publications

(9 citation statements)

References 62 publications

(22 reference statements)

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“…As shown in Scheme 23, the products 2-aryl-hydroquinolines and 2-aryl-2H-chromenes were successfully isolated in the yields up to 90% and the ee up to 95%, respectively, in the presence of chiral bisoxazoline ligands L6 or L7. [29] Scheme 23 Enantioselective Heck reactions of 1,4-dihydroquinolines and 4H-chromenes…”

Section: Scheme 22 Construction Of Axial and Central Chirality Via Hementioning

confidence: 99%

Recent Advances of Catalytic Enantioselective Heck Reactions and Reductive‐Heck Reactions

2021

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Heck reaction is one of the most important carbon‐carbon bond forming reactions with wide applications in organic synthesis. Considerable advances of enantioselective Heck reaction have been achieved in the past decades. This review focuses on recent development of catalytic asymmetric Heck reaction and reductive Heck reaction, which covers intermolecular and intramolecular versions since 2011. The article is organized in terms of the catalysts and olefin substrates.

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Section: Scheme 22 Construction Of Axial and Central Chirality Via Hementioning

confidence: 99%

Recent Advances of Catalytic Enantioselective Heck Reactions and Reductive‐Heck Reactions

2021

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“…In 2017, Hou's group reported the enantioselective synthesis of 2 H ‐flavenes via a palladium‐catalyzed asymmetric redox‐relay Heck reaction . Pd(CH 3 CN) 2 Cl 2 and PyrOx 42 were used as the catalyst for the reaction of 4 H ‐chromene 40 with phenylboronic acid 41 , after optimization, a series of chiral 2 H ‐flavenes were produced in good to high enantioselectivity (Scheme ).…”

Section: Asymmetric Synthesis Of 2h‐flavenesmentioning

confidence: 99%

Catalytic Asymmetric Syntheses of 2‐Aryl Chromenes

2019

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Chiral chromene motifs are important heterocycles in numerous natural products and bioactive molecules. Among them, flavenes, flavanes, and flavanones, which consist of the 2-aryl-chromene skeleton are observed most frequently. As subgroups of flavonoids, they often occur in various plants and show many biological activities, such as antitumor, antioxidant, antibacterial, anti-inflammatory, and anticoagulant properties. This Minireview summarizes recent reports on catalytic asymmetric synthesis of flavenes, flavanes, and flavanones. derivatives 1, giving the adduct 6. The subsequent intramolecular adol reaction and dehydration providing the desired product 3 (Scheme 2).Almost the same time, professor Córdova and coworkers presented the same domino reaction between 1 a and 2 catalyzed by 4 a, providing a series of 2H-flavenes in high yields and with 83-98% ees (Scheme 3). [5] Notably, by using 2nitrobenzoic acid as an additive, product 3 a could be obtained with 37% yield and 88% ee, comparing to 10% yield and 9% ee when adding no additives. More significantly, another additive, 4 Å molecular sieves, promoted the reaction significantly, increasing the product yield from 37% to 81% with no enantioselectivity erosion. The authors believed that the addition of an organic acid accelerated the adol condensation by activating the benzaldehyde. Also, the organic acid could stabilized the iminium intermediate, facilitating the oxa-Michael addition. The product 7 could be observed by NMR analysis, which gave an obvious evidence to the proposed reaction pathway (Scheme 2).By applying the similar approach, Wang and coworkers developed the asymmetric reaction of 1 and 2 catalyzed by organocatalyst 4 b. [6] Different from Córdova's condition, Wang found that Cl(CH 2 ) 2 Cl was the best solvent to provide the highest enantioselectivity. Lowering the reaction temperature improved ee with prolonged time for completion. The reaction had a broad scope and the functionalized 2H-flavenes were synthesized respectively high yields (53-98%) and with good to excellent levels of enantioselectivities (75-99% ee). However, the electronic nature of the α,β-unsaturated aldehydes 2 had a remarkable effect on the reactivities and ees that 2 bearing electron-withdrawing groups, such as nitro group, generally Scheme 2. Proposed mechanism of the organocatalytic asymmetric oxa-Michael addition/intramolecular adol reaction/dehydration cascade. Scheme 3. Direct organocatalytic asymmetric domino oxa-Michael/aldol condensations between 1 a and α, β-unsaturated aldehydes 2.

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“…[16] One of the best methods for the preparation of these heterocyclic compounds is multi-component reaction of aldehydes, kojic acid, and 1,3dicarbonyl compounds or malononitrile. Different catalysts were reported for these reactions, including palladium catalyst, [17] pyridinium-based salts, [18] Bi(OTf) 3 , [19] Fe 3 O 4 @SiO 2 , [20] magnetic ionic liquid, [21] CeCl 3 ⋅ 7H 2 O/SiO 2 , [22] ultrasonic irradiation, [23] Fe 3 O 4 @SiO 2 -AQ, [24] urea-based catalysts, [25] bifunctional tertiary amin [26] and NH 4 VO 3. [27] However, despite the efficiency of these methods, the development of less expensive and environmentally benign reaction conditions is a major goal for the synthesis of pyranopyran and chromene derivatives.…”

Section: Introductionmentioning

confidence: 99%

Dual Copper (II) Complex Supported on Diatomite as a Novel and Green Catalyst for the Synthesis of Dihydropyrano[3;2‐b]Chromenediones and Aminopyranopyrans

2021

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Immobilized copper (II) complex, namely, 2,2'-((1E,1'E)-((6-(l2azaneyl)-1,3,5-triazine-2,4-diyl)bis(azaneylylidene))bis (methaneylylidene))diphenol, supported on diatomite (Diatomite-Si-Pr-TAT-Bis-(AZY-MY)(Cu)Phenol) was introduced as a robust and heterogeneous catalyst for the synthesis of dihydropyrano[3;2-b]chromenediones and aminopyranopyrans. The Diatomite-Si-Pr-TAT-Bis-(AZY-MY)(Cu)Phenol catalyst was synthesized by complexation of copper (II) acetate with TAT-Bis-(AZY-MY)Phenol as a ligand with oxygen and nitrogen ligation sites that were anchored on diatomite through 3chloropropyltrimethoxysilane. The prepared catalyst was characterized using different microscopic and spectroscopic techni-ques including SEM, TEM, EDX, XRD, FT-IR, TGA and ICP. The diatomite is available and cheap support with a high specific surface area and a large amount of hydroxyl group on the surface. A large amount of dual copper (II) complexes were supported on diatomite through covalent bonds. The Diatomite-Si-Pr-TAT-Bis-(AZY-MY)(Cu)Phenol showed good catalytic activity for the synthesis of dihydropyrano[3;2-b] chromenediones and aminopyranopyrans using aromatic aldehyde, kojic acid, dimedone, or malononitrile. In addition, this catalyst system was reusable for five consecutive catalytic cycles without loss of their catalytic activity.

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Enantioselective Synthesis of Chromenes via a Palladium‐Catalyzed Asymmetric Redox‐Relay Heck Reaction

Cited by 15 publications

References 62 publications

Recent Advances of Catalytic Enantioselective Heck Reactions and Reductive‐Heck Reactions

Recent Advances of Catalytic Enantioselective Heck Reactions and Reductive‐Heck Reactions

Catalytic Asymmetric Syntheses of 2‐Aryl Chromenes

Dual Copper (II) Complex Supported on Diatomite as a Novel and Green Catalyst for the Synthesis of Dihydropyrano[3;2‐b]Chromenediones and Aminopyranopyrans

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