Transition‐Metal‐Free Approach to 4‐Ethynylpyrimidines via Alkenynones

Golubev, Pavel; Pankova, Alena S.; Кузнецов, М. А.

doi:10.1002/ejoc.201402045

Cited by 12 publications

(10 citation statements)

References 37 publications

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“…Moreover, regioselective processing of corresponding reactions is provided by imbalance of three electrophilic centers of cross-conjugated enynones . Combining the factors of high activity and selectivity allows development of effective methods for synthesis of a variety of heterocycles, such as for pyrrolone, 4-oxodihydrothiopyran, indole, pyrazole, pyrimidine, and other compounds with more complex structures . Just recently, the expansion of pent-1-en-4-yn-3-ones was balanced with operation of current methods of metal complex catalysis , as well as with application of superelectrophilic activation .…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Cross-Conjugated Enynones in Cyclocondensations with Hydrazines: Synthesis of Pyrazoles and Pyrazolines

et al. 2021

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The cyclocondensation of cross-conjugated enynones, dienynones, and trienynones (easily available due to low-cost starting compounds) with arylhydrazines leads to the regioselective synthesis of pyrazole derivatives (dihetaryl-substituted ethens, buta-1,3-diens, and hexa-1,3,5-triens) or results in 4,5-dihydro-1H-pyrazoles in good yield. The reaction path is controlled by the character of the substituent in enynone: the pyrazoles are obtained from the reaction of substrates that contain five-membered heteroaromatic substituents with arylhydrazines, and the 4,5-dihydro-1H-pyrazoles are obtained from the reaction of 1,5-diphenylpent-1-en-4-yn-3-one with arylhydrazines consistently. Despite the presence of a substituent, cyclocondensation of 2-hydrazinylpyridine with all of examined cross-conjugated enynones leads to the formation of pyrazoles. The reaction does not require special conditions (temperature, catalyst, inert atmosphere). The cyclocondensation pathways are determined by the electronic effect of an electron-rich five-membered heteroaromatic ring in the substrate. The synthesis allows use of various substituents and functional groups in enynone and hydrazine. The present method features high yields and simplicity of the product purification. The obtained pyrazoles possess fluorescent properties with a quantum yield up to 31%.

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Section: Introductionmentioning

confidence: 99%

Reactivity of Cross-Conjugated Enynones in Cyclocondensations with Hydrazines: Synthesis of Pyrazoles and Pyrazolines

et al. 2021

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“…We selected enynone 1a and 3(5)-(4-methylphenyl)-1 H -pyrazol-5(3)-amine ( 2c ) as model substrates for optimization of the reaction conditions. Previously, we showed that ethanol is the solvent of choice for reactions of enynones 1 with hydrazines and amidines, and therefore, the first experiment was carried out in ethanol at 80 °C in a sealed vessel. To our delight, no further optimization was needed because the single product was isolated in 85% yield (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…UV–vis spectra were recorded for 10 –5 M solutions in CHCl 3 , and extinction coefficients are given in parentheses. Preparation of enynones 1a – e was described previously …”

Section: Methodsmentioning

confidence: 99%

“…Over the past several years, we have been interested in the synthesis of ethynylated heterocyclic building blocks because acetylenes have emerged as extremely useful compounds for numerous transformations such as cross-coupling or click reactions. We reported earlier on synthesis of 2-aryl-1-ethoxy-5-(trimethylsilyl)pent-1-en-4-yn-3-ones 1 and demonstrated their applicability for the synthesis of ethynylated pyrazoles and pyrimidines . These results prompted us to use these enynones in reactions with pyrazolamines, which, if successful, would open straightforward access to ethynylated pyrazolo[1,5- a ]pyrimidines.…”

Section: Introductionmentioning

confidence: 96%

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Regioselective Synthesis of 7-(Trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines via Reaction of Pyrazolamines with Enynones

et al. 2016

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Condensation of enynones readily available from cheap starting material with pyrazolamines provides easy access to fluorescent 7-(trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines. The reaction is straightforward, does not require the use of any additional reagents or catalysts, and can be performed without inert atmosphere. Various substituents and functional groups in both enynone and pyrazolamine are tolerated. The presented method features full regioselectivity, high isolated yields, and simplicity of both setup and product purification. Fluorescent properties of the obtained pyrazolopyrimidines were studied.

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“…We have designed a straightforward method for the synthesis of 2-(trimethylsilylmethylene)pyrrol-3-ones bearing various substituents at 1- and 4-positions of the pyrrole core. The key starting compounds are cross-conjugated TMS-protected enynones 1 , readily available from bis(trimethylsilyl)acetylene and arylacetyl chlorides . Previously we thoroughly investigated the reactions of compounds 1 with binucleophiles, and herein we report the results obtained by employment of amines in reactions with enynones 1 .…”

Section: Introductionmentioning

confidence: 99%

Regioselective Transition-Metal-Free Synthesis of 2-(Trimethylsilylmethylene)pyrrol-3-ones by Thermal Cyclization of Acetylenic Enamines

2015

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Acetylenic enamines generated in situ from readily available enynones and primary amines undergo thermal cyclization in diphenyl ether providing easy access to 4-aryl-2-(trimethylsilylmethylene)-1,2-dihydro-3H-pyrrol-3-ones. This reaction is inherently versatile, allowing for variations of substituents in both enynone and amine. Full regioselectivity along with short reaction time (1-2 h) and simple workup afford single products in good to excellent isolated yields. Fluorescent properties of the obtained compounds were studied.

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Transition‐Metal‐Free Approach to 4‐Ethynylpyrimidines via Alkenynones

Cited by 12 publications

References 37 publications

Reactivity of Cross-Conjugated Enynones in Cyclocondensations with Hydrazines: Synthesis of Pyrazoles and Pyrazolines

Reactivity of Cross-Conjugated Enynones in Cyclocondensations with Hydrazines: Synthesis of Pyrazoles and Pyrazolines

Regioselective Synthesis of 7-(Trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines via Reaction of Pyrazolamines with Enynones

Regioselective Transition-Metal-Free Synthesis of 2-(Trimethylsilylmethylene)pyrrol-3-ones by Thermal Cyclization of Acetylenic Enamines

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