Construction of Chiral Multi‐Functionalized Polyheterocyclic Benzopyran Derivatives by Using an Asymmetric Organocatalytic Domino Reaction

Guo, Zhiwei; Li, Xinsheng; Zhu, Weidong; Xie, Jian‐Hua

doi:10.1002/ejoc.201200928

Cited by 43 publications

(18 citation statements)

References 48 publications

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“…1); the stereochemistry of 5 was confirmed by the crystallographic analysis. 11 This indicated that in the case of 2b spontaneous aromatization does not proceed.…”

Section: Resultsmentioning

confidence: 98%

“…10 Xie et al obtained the dibenzo [b,d]pyrans by the domino reaction starting from 2-aryl-3-nitro-2H-chromenes and ylidenemalononitriles. 10,11 This promising approach deserves further investigations in order to expand the scope of its possible applications. 12 Herein we wish to demonstrate utility of readily available 3-nitro-2-(trifluoromethyl)-2H-chromenes 1 as valuable building blocks for the construction of dibenzo [b,d]pyrans bearing a CF 3 group at the 6-position via a formal [4þ2] cycloaddition of 2-(1-phenylethylidene)malononitrile (2a) and 2-(1-phenylpropylidene)malononitrile (2b).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

2013

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“…1); the stereochemistry of 5 was confirmed by the crystallographic analysis. 11 This indicated that in the case of 2b spontaneous aromatization does not proceed.…”

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

2013

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“…To the best of our knowledge this is the first example of a catalytic enantioselective access to spirocyclic cyclohexenimines, expanding the arena of pyrazolinone based spirocyclohexane derivatives, potentially useful in medicinal chemistry. [27] Mild reaction conditions, commercial availability of the organocatalyst and feasibility of scale-up process are other attractive features of the process.…”

Section: Abstract: Asymmetric Synthesis; Organocatalysis; Spirocyclicmentioning

confidence: 99%

Asymmetric Synthesis of Pyrazolone Fused Spirocyclohexeneimines via a Vinylogous Michael/Cyclization Cascade Reaction

2018

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Diastereoisomeric pyrazolone-fused spirocyclohexenimines, bearing contiguous all-carbon quaternary and tertiary stereocenters, are readily synthesized for the first time in good to excellent yield (up to 98%) and high enantioselectivity (up to 97% ee) via vinylogous Michael reaction/cyclization cascade reaction of a-arylidene pyrazolones and a,a-dicyanoalkylidenes. The formal [4 + 2] atom-economical annulation proceeds with commercially available Takemoto's catalyst under mild reaction conditions. Scale-up reaction and posttransformation of the products were also demonstrated.The interest of chemists toward the asymmetric synthesis of spirocyclic compounds constantly increased in the last decade. [1] This is a highly challenging goal in organic synthesis as the quaternary stereocenter links two cyclic compounds, often decorated with additional tertiary or quaternary stereocenters, whose stereochemistry has to be controlled. Most of these studies were inspired by natural and synthetic bioactive compounds, bearing heterocyclic and carbocyclic units, with the idea to create new hybrid spirocylic compounds of potentially widespread biological activities. Among the classes of spirocyclic compounds, those bearing the pyrazolone unit and the carbocyclic cyclohexane, [2] cyclohexanone, [3] cyclohexenone [4] and cyclohexadiene rings, [5] have attracted considerable interest due to their relevance in medicinal chemistry ( Figure 1). [6] Some selected examples, illustrated in Figure 1, showed that these compounds display diverse and valuable biological activities as phosphodiesterase inhibitor, [2b] antimicrobial, [3a] anticancer [4] and antiinflammatory agents. [7] From a synthetic point of view, the methodologies designed to prepare these compounds essentially relied on organocatalytic cascade double Michael reaction or double Michael reaction followed by aldol reaction. [8] These practical approaches successfully guaranteed mild and environment friendly conditions as well as high control of the stereoselectivity. In this context, a-alkylidene pyrazolinones have been used as Michael acceptors to obtain a few complex spirocyclic cyclohexane derivatives, bearing quaternary and tertiary stereocenters, as demonstrated by the groups of Rios, [9] Wang [3c,10] and Enders [11] (Scheme 1). The organocatalytic approaches were successfully developed using popular Hayashi-Jørgensen's catalyst and Cinchona alkaloids derived primary or tertiary amines. Very recently, Biju [12] and Li [13] applied a less inves-Figure 1. Representative examples of bioactive spiropyrazolones containing six-membered rings.

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“…1). Alkylidene malononitriles [15][16] can serve as four-carbon starting materials for the synthesis of cyclic compounds. With the ongoing interest in the construction of valuable aromatic polycyclic compounds using electron-deficient heteroaromatics, [17] we envisioned that the dibenzofuran derivatives 3 could be synthesized via a base promoted benzannulation [18] of 2-nitrobenzofurans 1 with alkylidene malononitriles 2 (Scheme 1B, eq.…”

Section: Introductionmentioning

confidence: 99%

“…[13c-d] The structure of product was further confirmed by the X-ray analysis of a single crystal of 3 ea (See Supporting Information). [23] Based on the experimental results and previous studies, [13,[15][16] the mechanism proposed for the synthesis of dibenzofuran derivatives 3 is shown in Scheme 4. The alkylidene malononitriles 2 was initially deprotonated by K 2 CO 3 to yield anion A, which reacted with 2-nitrobenzofurans 1 via vinylogous conjugate addition and cyclization cascade to produce the intermediate B.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Dibenzofurans Derivatives via Benzannulation of 2‐Nitrobenzofurans and Alkylidene Malononitriles

Cao

Chen

et al. 2020

Asian J Org Chem

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Although various methods for the preparation of dibenzofurans are available, an efficient, general synthesis of dibenzofurans from benzofurans remains an unsolved problem. Herein, we provide the first benzannulation of readily prepared 2-nitrobenzofurans with alkylidene malononitriles. This methodology enables facile assembly of a wide variety of highly functionalized dibenzofurans in moderate to excellent yields under metal-free conditions. Gram-scale synthesis and further elaborations of the product were succesfully performed, demonstrating synthetic utility of this method.

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Construction of Chiral Multi‐Functionalized Polyheterocyclic Benzopyran Derivatives by Using an Asymmetric Organocatalytic Domino Reaction

Cited by 43 publications

References 48 publications

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

Asymmetric Synthesis of Pyrazolone Fused Spirocyclohexeneimines via a Vinylogous Michael/Cyclization Cascade Reaction

Synthesis of Dibenzofurans Derivatives via Benzannulation of 2‐Nitrobenzofurans and Alkylidene Malononitriles

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