Synthesis of 2-phosphonylated imidazo[1,2-a]pyridines under catalyst-free conditions

Krylov, A. S.; Kaskevich, K. I.; Erkhitueva, E. B.; Svintsitskaya, N. I.; Догадина, А. В.

doi:10.1016/j.tetlet.2018.10.052

Cited by 14 publications

(4 citation statements)

References 29 publications

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“…Anhydrous K 2 CO 3 was used as a base to neutralize HCl formed during the reaction. The need for the use of anhydrous solvents and reagents is caused by the possibility of the formation of byproducts, if any, due to hydrolysis as we have noted earlier in the case of the reactions of chloroethynylphosphonates with nitrogen-containing nucleophiles [ 37 – 39 ].…”

Section: Resultsmentioning

confidence: 99%

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

Kaskevich¹,

Babushkina²,

Gurzhiy³

et al. 2020

Beilstein J. Org. Chem.

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A series of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines was synthesized for the first time by the reactions of chloroethynylphosphonates with unsubstituted and 5(6)-substituted 2-thiouracils. The reaction of chloroethynylphosphonates with 6-substituted 2-thiouracils bearing electron-donor groups (CH3, Ph) proceeded with high regioselectivity involving the cyclization through the N3-nitrogen atom to form new 3-phosphonylated thiazolo[3,2-a]-5-oxopyrimidines with good yield. In the case of unsubstituted and 5-methyl-2-thiouracils, cyclization occurred predominantly through the N1 atom and partially via the N3-nitrogen atom to form a mixture of the corresponding thiazolo[3,2-a]-7- and 5-oxopyrimidines. A dramatic change in the reaction regioselectivity was observed in the case of 6-trifluoromethyl-2-thiouracil that afforded 2- and 3-phosphonylated 5-oxothiazolopyrimidines in a 1:1 ratio.

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Section: Resultsmentioning

confidence: 99%

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

Kaskevich¹,

Babushkina²,

Gurzhiy³

et al. 2020

Beilstein J. Org. Chem.

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“…Note the reactions of 2-hydrazinylpyridines 1a – f with chloroethynylphosphonates 2 afforded the title [1,2,4]triazolo[4,3- a ]pyridines 3 – 8 in an almost quantitative yield. It should be emphasized that in the case of 2-hydrazinylpyridines the reaction selectivity is higher than in a similar reaction with 2-aminopyridines, where the formation of trace amounts of the corresponding amidines and amides was observed [4]. Moreover, the formazan-type products, the formation of which was observed in reactions of chloroethynylphosphonates with arylhydrazines, were not detected [16].…”

Section: Resultsmentioning

confidence: 99%

“…The obtained new compounds are of special interest due to the practical utility of the formed fused heterocycles, such as indoles [1], thiazolo[2,3- b ][1,3,4]thiadiazole [2], and benzo[4,5]imidazo[2,1- b ]thiazole [3], as well as due to the simultaneous presence of a biologically active phosphorus function in the molecules. Recently, we have shown that the reaction of chloroethynylphosphonates with 2-aminopyridines proceeds through a 5- endo - dig cyclization to form imidazo[1,2- a ]pyridines [4]. In continuation of this study, herein we report an effective approach to the synthesis of new phosphonylated triazolopyridine derivatives by reacting chloroethynylphosphonates with 2-hydrazinylpyridines.…”

Section: Introductionmentioning

confidence: 93%

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

Krylov

Petrosian

Piterskaya

et al. 2019

Beilstein J. Org. Chem.

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A series of novel 3-methylphosphonylated [1,2,4]triazolo[4,3-a]pyridines was accessed through a 5-exo-dig-type cyclization of chloroethynylphosphonates and commercially available N-unsubstituted 2-hydrazinylpyridines. In addition, 3-methylphosphonylated [1,2,4]triazolo[4,3-a]quinolines and 1-methylphosphonylated [1,2,4]triazolo[3,4-a]isoquinolines were synthesized in a similar manner. The presence of a NO2 group in the starting hydrazinylpyridine induces a Dimroth-type rearrangement leading to 2-methylphosphonylated [1,2,4]triazolo[1,5-a]pyridines.

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“…A successful catalyst-free and simple approach for the regio- and chemoselective synthesis of novel 2-phosphonylated imidazo[1,2- a ]pyridines 33 from 2-aminopyridine and phosphorylated alkynes under mild conditions was developed by Krylov et al ( Scheme 10 ). 19 It is assumed that the transformation includes an initial attack of the pyridine nitrogen atom at the triple bond, followed by hydrogen chloride cleavage and ring closure.…”

Section: Recent Metal-free Protocolsmentioning

confidence: 99%

Recent Progress in Metal-Free Direct Synthesis of Imidazo[1,2-a]pyridines

Kurteva

2021

ACS Omega

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This Mini-Review highlights the most effective protocols for metal-free direct synthesis of imidazo[1,2- a ]pyridines, crucial target products and key intermediates, developed in the past decade. The emphases is given on the ecological impact of the methods and on the mechanistic aspects as well. The procedures efficiently applied in the preparation of important drugs and promising drug candidates are also underlined.

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Synthesis of 2-phosphonylated imidazo[1,2-a]pyridines under catalyst-free conditions

Cited by 14 publications

References 29 publications

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

Recent Progress in Metal-Free Direct Synthesis of Imidazo[1,2-a]pyridines

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