Metal-Free Insertion Reactions of Diazo Carbonyls to Azlactones

Mello, Amanda C. de; Momo, Patrícia B.; Burtoloso, Antonio C. B.; Amarante, Giovanni W.

doi:10.1021/acs.joc.8b01683

Cited by 8 publications

(6 citation statements)

References 43 publications

(54 reference statements)

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“…Azlactones (or oxazol-5-ones) are valuable structures in organic synthesis; they have numerous reactive sites, allowing a wide variety of organic transformations such as dynamic kinetic resolution (DKR), 2 Michael reactions, 3 1,6-additions 4 and insertion reactions, 5 and can serve as linkers for click chemistry, 6 to name but a few. Furthermore, azlactones have key pharmacological activities that include antioxidant, antiparasitic, antibiotic and antimicrobial, and are used as herbicides and pesticides.…”

Section: Table 1 Effect Of Different Solvents and Alcoh...mentioning

confidence: 99%

Dynamic Kinetic Resolution of Azlactones by Bifunctional Thioureas with α‑Trifluoromethyl or Methyl Groups

Jiménez

Cantú-Reyes

Flores-Ramos

et al. 2022

Synlett

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The asymmetric ring opening of azlactones via dynamic kinetic resolution (DKR) is investigated by contrasting thioureas incorporating 1-arylethyl substituents against their more acidic trifluoromethylated analogs. All the catalysts under study outperform Takemoto’s thiourea because of the inclusion of an additional chiral center. However, the difference in yield and selectivity between the fluorinated and non-fluorinated catalysts is minimal. We explain this observation by analysis of calculated transition states. Our findings show that the hydrogen bond (HB) between the NH linked to the 1-arylethyl and the negatively charged oxygen in the benzyloxy ion is the longest in the HB network, whereas the HB between the ammonium group and the same oxygen atom is the shortest. Thus, the substituents and the HB donor ability of this chiral fragment attached to the thiourea are not important in the reaction.

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Section: Table 1 Effect Of Different Solvents and Alcoh...mentioning

confidence: 99%

Dynamic Kinetic Resolution of Azlactones by Bifunctional Thioureas with α‑Trifluoromethyl or Methyl Groups

Jiménez

Cantú-Reyes

Flores-Ramos

et al. 2022

Synlett

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“…Flash column chromatography was carried out using 200–300 mesh silica gel. All of the azlactones ( 1a,b,c,d,e , g, 1i ) and ketimines ( 2a,b,c,f,g,j,k,l , 2h , 2i , 2m ,) used in this work were synthesized according to known protocols.…”

Section: Experimental Sectionmentioning

confidence: 99%

Squaramide-Catalyzed Asymmetric Mannich Reactions of Azlactones with Isatin-Derived Ketimines: Access to α,β-Diamino Acid Derivatives Bearing Vicinal Quaternary Stereocenters

Peng

et al. 2020

J. Org. Chem.

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A highly stereoselective Mannich reaction of α-amino acid derived azlactones with isatin-derived ketimines enabled by a chiral bifunctional squaramide organocatalyst is reported, affording α,β-diamino acid derivatives bearing vicinal quaternary stereocenters in moderate to good yields (40–95%), moderate to excellent diastereoselectivities (3:1 → 20:1), and good to excellent enantioselectivities (66–97%). This reaction can be readily performed on gram scale, and the Mannich adduct could be easily converted to the corresponding α,β-diamino ester via simple operations.

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“…The development of non‐classical protocols involving azlactone rings is also of great interest to the organic chemistry community. In this context, our research group described in 2018 the Brønsted base mediated insertion of diazo carbonyls ( 200 ) to azlactones ( 199 ), affording O ‐alkylated oxazol derivatives ( 201 ) (Scheme ) . This protocol employed stoichmetric DIPEA and allowed the access to the desired derivatives in good to excellent yields (ranging from 74 to 98 %).…”

Section: Conjugate Additions and Other Enolate‐mediated Reactionsmentioning

confidence: 99%

Recent Advances in Azlactone Transformations

2019

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Azlactones, also known as oxazolones, are versatile building blocks in organic synthesis due to the presence of multiple pro‐nucleophilic and electrophilic reactive sites. Recently, several elegant organo‐ and metal‐catalyzed studies have been described, allowing the stereocontrolled access to complex structures in only one or a few chemical steps. Moreover, the development of one‐pot, tandem and domino reactions greatly enhanced the azlactone scaffold potential. In this context, this review aims to cover novel methodologies, including a brief overview of oxazolones and Erlenmeyer azlactones preparation. New approaches towards classical reactions, such as dynamic kinetic resolution, cycloadditions, and conjugate additions will be presented as well as new methodologies involving photochemical and flow chemistry technology. Finally, for most studies, selected examples will be presented and mechanistic pathways and/or activating modes will be carefully discussed.

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Metal-Free Insertion Reactions of Diazo Carbonyls to Azlactones

Cited by 8 publications

References 43 publications

Dynamic Kinetic Resolution of Azlactones by Bifunctional Thioureas with α‑Trifluoromethyl or Methyl Groups

Dynamic Kinetic Resolution of Azlactones by Bifunctional Thioureas with α‑Trifluoromethyl or Methyl Groups

Squaramide-Catalyzed Asymmetric Mannich Reactions of Azlactones with Isatin-Derived Ketimines: Access to α,β-Diamino Acid Derivatives Bearing Vicinal Quaternary Stereocenters

Recent Advances in Azlactone Transformations

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