Catalyst and base free aza-Michael addition reaction: Synthesis of poly-substituted 4-pyrazole based benzopyrans

Das, T. P.; Mohapatra, Seetaram; Mishra, Nilima Priyadarsini; Nayak, Smita

doi:10.1016/j.tetlet.2022.153762

Cited by 8 publications

(8 citation statements)

References 59 publications

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“…There are only few examples of non‐catalyzed conjugate addition of pyrazoles to electron‐deficient alkenes, especially ones bearing a nitro group. Thus, the aza‐Michael reaction of 2‐aryl‐3‐nitro‐ 2H ‐chromenes 11 with pyrazole, 3‐methyl‐ or 4‐bromopyrazole furnishes target adducts 12 under mild conditions (room temperature, THF) in good yields (69–84%) [12] . Imidazole do not react at all under optimal reaction conditions (Scheme 1).…”

Section: Pyrazoles Imidazoles Triazoles and Tetrazolesmentioning

confidence: 99%

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Weak Nucleophiles in the Aza‐Michael Reaction

Rulev

2023

Adv Synth Catal

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The 1,4‐conjugated addition of nitrogen centered nucleophiles to electron‐deficient alkenes is one of the most significant and widely used reactions in modern synthetic organic chemistry. To date, various protocols for the aza‐Michael reaction have been developed. However, these reports mainly focus on the use of strong Michael donors. In recent years, the conjugate addition of weak nitrogen nucleophiles to various Michael acceptors gained increasing popularity. Impressive progress in this area has been achieved by the use of more efficient catalyst systems. This review aims to provide a critical analysis of the results obtained in reactions of weak nucleophiles (azoles, pyrroles, indoles, carbamates, purines, amides, hydrazides, uraciles etc) with electron‐deficient alkenes which were reported over the past twelve years.

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Section: Pyrazoles Imidazoles Triazoles and Tetrazolesmentioning

confidence: 99%

“…Thus, the aza-Michael reaction of 2-aryl-3-nitro-2H-chromenes 11 with pyrazole, 3-methyl-or 4-bromopyrazole furnishes target adducts 12 under mild conditions (room temperature, THF) in good yields (69-84%). [12] Imidazole do not react at all under optimal reaction conditions (Scheme 1).…”

Section: Pyrazoles Imidazoles Triazoles and Tetrazolesmentioning

confidence: 99%

Weak Nucleophiles in the Aza‐Michael Reaction

Rulev

2023

Adv Synth Catal

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“…High yield and high functional group tolerance are the significance of this methodology (Scheme 32). [91] …”

Section: Michael Addition Reactions Under Catalyst‐free and Base‐free...mentioning

confidence: 99%

Recent Advances of Michael/hetero‐Michael Addition Reaction in the Synthesis of 3‐Nitro‐2H‐chromene Derivatives

et al. 2023

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3‐Nitro‐2H‐chromene and derivatives are the significant structural building blocks of many natural products and pharmacologically active compounds. So, great deals of effort have been made for the development and improvement of 3‐nitro‐2H‐chromene functionalized scaffolds by utilizing different methodologies. Among the various strategies, Michael/hetero‐Michael addition reactions to 3‐nitro‐2H‐chromene have been established as the most vibrant and unique research area for the construction of diverse C−C and C−X (X=heteroatoms) bonds providing versatile 2H‐chromene frameworks. In recent years, a broad range of efficient Michael donors has been explored extensively which motivates the scientific community to work on these useful 2H‐chromene frameworks in presence of different bases, transition metals, organocatalysts, and base/catalyst‐free conditions. Considering the importance of this research field, the present review highlights the major advancements of Michael/hetero‐Michael addition reaction to 3‐nitro‐2H‐chromenes utilizing various Michael donors from the year 2010 to 2022 in a comprehensive manner.

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“…2 To overcome this limitation, various metal catalysts, inorganic supports, organocatalysts, acids, and bases have been studied and successfully used for the conjugate addition of azoles to electron-deficient alkenes. 3…”

Section: Introductionmentioning

confidence: 99%