Enantioselective synthesis of fused dihydropyranones via squaramide-catalyzed Michael addition/lactonization cascade reaction

Xian, Jialing; Chen, Lin; Ye, Ling; Sun, Yin; Shi, Zhichuan; Zhao, Zhigang; Li, Xuefeng

doi:10.1016/j.tet.2019.03.007

Cited by 11 publications

(6 citation statements)

References 78 publications

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“…Michael addition by enolate generated from βdiketone to the enone and follow up O-cyclization would accomplish the overall annulation cascade to deliver the products 180 with notable yields and enantioselectivities. [70] The reaction was well compatible with cyclic 1,3-diketo substrates to deliver the δ-lactone as a part of fused bicycle 180. Two examples were shown with acyclic 1,3-diketones (Scheme 46b).…”

Section: Synthesis Of Oxacyclesmentioning

confidence: 94%

“…Li and co‐workers demonstrated C catalyzed cascade between 1,3‐diketones 178 and α , β ‐unsaturated N ‐acyl heterocycles 179 in course of synthesizing optically active δ ‐lactone. Michael addition by enolate generated from β ‐diketone to the enone and follow up O ‐cyclization would accomplish the overall annulation cascade to deliver the products 180 with notable yields and enantioselectivities [70] . The reaction was well compatible with cyclic 1,3‐diketo substrates to deliver the δ‐lactone as a part of fused bicycle 180 .…”

Section: Synthesis Of Six Membered Ringsmentioning

confidence: 99%

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Squaramide Catalyzed Asymmetric Synthesis of Five‐ and Six‐Membered Rings

Biswas¹,

Ghosh

Shankhdhar

et al. 2021

Asian J Org Chem

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Chiral analogues of squaramides have been fruitful in organocatalyzed asymmetric reactions over last decade. Alongside other H-bonding catalysts like ureas, thioureas: squaramides have been proved to be efficient asymmetric catalysts for the formation of acyclic and cyclic chiral molecules. A wide range of cyclic molecules bearing multiple functionalities and stereocenters have been synthesized by using several bifunctional squaramides as catalysts. These catalysts perform as base utilizing basic N atom in their chiral extension and help in stereoinduction by forming H-bonds with suitable H-bond acceptors. The present review focuses on assembling recent progresses of asymmetric synthesis of five and six membered rings promoted by squaramides. A handful of articles have been published by several research groups documenting asymmetric construction of five-and six-membered rings as part of interesting and complex molecular architectures. Different methodologies like conventional and formal cycloadditions or cascade reactions have been engineered through the assistance of chiral squaramides to fabricate the carbo-and heterocycles. This review also includes dual and cooperative catalytic system in which squaramide is one of the catalysts.

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Section: Synthesis Of Oxacyclesmentioning

confidence: 94%

Section: Synthesis Of Six Membered Ringsmentioning

confidence: 99%

Squaramide Catalyzed Asymmetric Synthesis of Five‐ and Six‐Membered Rings

Biswas¹,

Ghosh

Shankhdhar

et al. 2021

Asian J Org Chem

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“…The same group, more recently, employed α,βunsaturated N-acyl heterocycles, including α,β-unsaturated pyrazoleamides, in a domino approach for the synthesis of biologically interesting heterocycles, exploiting a Michael reaction/lactonisation sequence (Scheme 3). [15] The fused dihydropyranones were isolated in good to high yield, after prolonged reaction times, when treating dimedone and pyrazoleamides in the presence of 20 mol% of squaramide 2 a. The nature of the heterocycle in the α,β-unsaturated amides played a crucial role in both the reaction steps (Schemes 3 and 4).…”

Section: Pyrazoleamides As Electrophiles In Organocatalysismentioning

confidence: 99%

Pyrazoleamides in Catalytic Asymmetric Reactions: Recent Advances

et al. 2021

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Pyrazoleamides are a class of compounds which have received significant attention in the last years in asymmetric catalysis as more reactive and practical surrogates of esters or amides. These readily available reagents have served in a variety of diastereo-and enantioselective metal-and organocatalytic transformations, spanning from simple carbon-carbon or carbon-heteroatom bond formation to cascade and rearrangement reactions, to produce valuable classes of heterocyclic compounds. More recently, pyrazoleamides have proved to be pertinent reagents in asymmetric catalysis merged with photoredox catalysis, and in more challenging stereoselective bond-forming reactions, occurring directly from a visible-light activated substrate/catalyst complex without any charge separation. Both strategies enable new activation concepts useful for the production of difficult-to-access intermediates and pharmaceuticals. In this review, an overview of the progress achieved in asymmetric catalytic reactions of pyrazoleamides from 2015 up to middle 2020, is illustrated. Rearrangements of α-Diazo Pyrazoleamides 7. Combined Metal-and Organocatalysis 8. Pyrazoleamides in Visible-Light-Activated Photochemical Reactions 8.1. Merging Visible Light Photoredox Activation with Asymmetric Catalysis 8.2. Stereocontrolled Direct Photoreactions from Electronically Excited State 8.3. Merging HAT Photocatalysis with Chiral Lewis Acid Catalysis 9.

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“…For example, Rueping et al demonstrated that the cyclohexane-1,3-dione undergoes a cascade reaction with α,β-unsaturated aldehydes [4] and they later employed the method to synthesise indoloquinolizidines [5]. Moreover, six-membered and five-membered cyclic 1,3-diketones have been investigated in reactions with acetates of nitroalkenes [6], cyanoacrylates and benzylidene malononitriles [7], ortho-hydroxy-benzhydryl alcohols [8], α,β-unsatu-rated pyrazolamides [9] and, 2-oxobut-3-enoates [10]. A 1,2dicarbonyl moiety is also an important structural fragment present in various natural products and biologically active compounds [11].…”

Section: Introductionmentioning

confidence: 99%