Iodine-Catalyzed Iso-Nazarov Cyclization of Conjugated Dienals for the Synthesis of 2-Cyclopentenones

Marsili, Lucía A.; Pergomet, Jorgelina L.; Gandon, Vincent; Riveira, Martín J.

doi:10.1021/acs.orglett.8b03229

Cited by 21 publications

(34 citation statements)

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“…20 While the corresponding Nazarov products obtained from 7 are key intermediates for the synthesis of germination stimulants for seeds of the parasitic plant Orobanche aegyptiaca, 21 the Nazarov cyclization of 9b could result in the natural product bruceolline E. 22 Scheme 3. Selected Examples for Polarized Nazarov and a Related Iso-Nazarov Cyclizations 15a−d, 18 Scheme 4. Synthesis of the Nazarov Systems a Solvent Screening.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…9,17 Recently, iodine has already been applied as a catalyst in the related iso-Nazarov reactions with 5 mol % catalyst loading in boiling ethyl acetate (Scheme 3). 18 In this mechanistically similar reaction, the alkene attacks the activated carbonyl group, and the final cyclopentenone is obtained after isomerization of the double bond. We now report on our results on iodine-catalyzed Nazarov cyclizations and their mechanistic investigations.…”

Section: ■ Introductionmentioning

confidence: 99%

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Iodine-Catalyzed Nazarov Cyclizations

et al. 2019

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The Nazarov cyclization is an important pericyclic reaction that allows the synthesis of substituted cyclopentenones. We now demonstrate that this reaction can be performed under very mild, metal-free reaction conditions using molecular iodine as the catalyst. A variety of different divinyl ketones including aromatic systems undergo the iodine-catalyzed reaction with moderate to very good yields in both polar and apolar solvents. Our mechanistic studies indicate that the Nazarov system is activated through a halogen bond between the carbonyl group and the catalyst, and other modes of action like Brønsted acid or iodonium ion catalysis are unlikely. Furthermore, addition of iodine to the double bond or a putative iodine-catalyzed cis–trans isomerization of the employed olefins seem not to be an important side reaction here.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Iodine-Catalyzed Nazarov Cyclizations

et al. 2019

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“…The XB-catalyzed Nazarov cyclization attracted much attention recently [54,83,84]. Breugst and co-workers reported a combined experimental and computational study of I 2 -catalyzed Nazarov cyclization [84].…”

Section: -Catalyzed Iso-nazarov Cyclization Of Conjugated Dienalsmentioning

confidence: 99%

“…Riveira and coworkers recently studied a similar I 2 -catalyzed iso-Nazarov cyclization of conjugated dienals at the PCM (ethyl acetate)/M06-2X/6-311+G(d,p) (aug-cc-pVTZ-PP basis set for I) level ( Figure 9) [83]. The reaction barrier (∆G 393 ) of I 2 -catalyzed cyclization of 31a was computed to be quite high at 29.9 kcal/mol, although it is lower than the barrier of the uncatalyzed reaction at 38.1 kcal/mol.…”

Section: -Catalyzed Iso-nazarov Cyclization Of Conjugated Dienalsmentioning

confidence: 99%

Application of Halogen Bonding to Organocatalysis: A Theoretical Perspective

Hui

Wong

2020

Molecules

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The strong, specific, and directional halogen bond (XB) is an ideal supramolecular synthon in crystal engineering, as well as rational catalyst and drug design. These attributes attracted strong growing interest in halogen bonding in the past decade and led to a wide range of applications in materials, biological, and catalysis applications. Recently, various research groups exploited the XB mode of activation in designing halogen-based Lewis acids in effecting organic transformation, and there is continual growth in this promising area. In addition to the rapid advancements in methodology development, computational investigations are well suited for mechanistic understanding, rational XB catalyst design, and the study of intermediates that are unstable when observed experimentally. In this review, we highlight recent computational studies of XB organocatalytic reactions, which provide valuable insights into the XB mode of activation, competing reaction pathways, effects of solvent and counterions, and design of novel XB catalysts.

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“…The catalytic hydroformylation of conjugated enynes is an attractive synthetic route for the preparation of 2,4-dienal, which is a versatile building block in organic synthesis . However, the existing enyne hydroformylation systems are limited to the conjugated enynes with an internal CC bond .…”

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confidence: 99%

Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand

et al. 2021

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The hydroformylation of terminal arylalkynes and enynes offers a straightforward synthetic route to the valuable (poly)enals. However, the hydroformylation of terminal alkynes has remained a long-standing challenge. Herein, an efficient and selective Rh-catalyzed hydroformylation of terminal arylalkynes and conjugated enynes has been achieved by using a new stable biphosphoramidite ligand with strong π-acceptor capacity, which affords various important E-(poly)enals in good yields with excellent chemo-and regioselectivity at low temperatures and low syngas pressures.

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Iodine-Catalyzed Iso-Nazarov Cyclization of Conjugated Dienals for the Synthesis of 2-Cyclopentenones

Abstract: Molecular iodine was identified as an efficient catalyst for the cycloisomerization of conjugated dienals to substituted 2-cyclopentenones. DFT calculations suggested an unexpected concerted character for this cyclization.

Cited by 21 publications

References 67 publications

Iodine-Catalyzed Nazarov Cyclizations

Iodine-Catalyzed Nazarov Cyclizations

Application of Halogen Bonding to Organocatalysis: A Theoretical Perspective

Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand

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