Transformations of Substituted Oxazolo- [3,2-a]Pyridines to 5,6-Disubstituted Indolizines: Synthesis And X-ray Structural Mapping

Rybakov, Victor B.; Бабаев, Е. В.

doi:10.1007/s10593-014-1465-8

Cited by 7 publications

(3 citation statements)

References 19 publications

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“…Alkylation (and phenacylation) of pyridin-2-ones may occur either at Nor O-atoms [9]. Based on the literature data of reaction of phenacyl bromides with 4,6-dimethylpyridin-2-ones (bearing electron withdrawing group CN, CONH 2 , CO 2 R at C-5) [6,7,[15][16][17][18]) we expected that alkylation of sodium salts of 6-methyl-beta-nitropyridin-2-ones (1a-d) would also proceed at the nitrogen atom. As an additional argument, Na-salt of 5-nitropyridin-2-one also underwent N-phenacylation [19].…”

Section: Attempts Of Direct Phenacylation Of Homologues Of Beta-nitromentioning

confidence: 99%

Phenacylation of 6-Methyl-Beta-Nitropyridin-2-Ones and Further Heterocyclization of Products

Бабаев

Rybakov

2020

Molecules

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Reaction between the derivatives of 6-methyl-beta-nitropyridin-2-one and phenacyl bromides was studied, and the yields observed were extremely low. The pyridones were converted via chloropyridines to methoxyderivatives, which were N-phenacylated. N-Phenacyl derivatives of 4,6-dimethyl-5-nitropyridin-2-one under the action of base gave 5-hydroxy-8-nitroindolizine and under acidic conditions gave 5-methyl-6-nitrooxazole[3,2-a]pyridinium salt, which underwent recycization with MeONa to 5-methoxy-8-nitroindolizine.

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Section: Attempts Of Direct Phenacylation Of Homologues Of Beta-nitromentioning

confidence: 99%

Phenacylation of 6-Methyl-Beta-Nitropyridin-2-Ones and Further Heterocyclization of Products

Бабаев

Rybakov

2020

Molecules

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“…6,7 In the current work, we utilized the easily accessible homolog 3-cyanopyridin-2-one, which we succeeded in turning into an oxazolopyridinium salt 3b by phenacylation and subsequent cyclocondensation by a method developed by us previously. 7 Using the sodium salt of the precursor cyanopyridone (promotes alkylation at the nitrogen atom), and carrying out the reaction in an ion-solvating solvent (e.g., DMF) was expected to increase the yield of N-alkylated isomer 4b. Despite the low yield of compound 4b (and the formation of the O-alkylation by-product 4a) in the first step, we found this method convenient since it does not require the use of chromatography and can be done in a larger scale.…”

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confidence: 99%

“…The hydrolysis of the cyano group is possible in this case; however, the cyclization proceeded to completion by the action of the acid for 30 min and no hydrolysis was observed (as in the case of a p-bromophenyl derivative). 7 For recyclization of salt 3b, N-(methylamino)acetaldehyde dimethyl acetal and an ester of sarcosine were selected as the secondary amines. Recyclization was conducted by heating under reflux with an excess of the amine (Scheme 3).…”

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Rearrangement of oxazolo[3,2-a]pyridines as an approach of synthesizing aza[3.3.2]cyclazines

Бабаев

Nevskaya

Dlynnikh

2015

Chem Heterocycl Comp

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Evolution of the theory of aromaticity has raised interest in the synthesis of pericondensed indolizines such as cyclazines 1 and their analogs. 1 Yet, chemistry of hetero counterparts of such structures, including antiaromatic ones, are still poorly understood. Figure 1 shows the currently known representatives of [3.3.2]cyclazine series 1a-i. 2 The synthesis of such cyclazines includes addition of a five-and/or six-membered ring, 2 in accordance with cylization schemes shown in Figure 2.Theoretically, indolizines 2 containing a heteroatom at position 5 could serve as precursors of [3.3.2]cyclazines, but these compounds are not readily available. Our research group has developed a new strategy for the synthesis of 5-substituted indolizines by recyclization of oxazolopyridinium salts 3 by the action of nucleophiles (amines and alkoxides). 3 The use of bifunctional reagents (Nu -a nucleophilic heteroatom, E -an electrophilic carbon atom) in such a reaction could lead to indolizines 2, potentially capable of cyclization into cyclazine 1 analogs via attack by an electrophilic atom on the π-excessive pyrrole moiety (Scheme 1).Amine derivatives having a carbonyl group at the chain end could serve as suitable reagents. Of course, such agents must be stable under recyclization conditions (high temperature and concentration of the reagents). Of secondary amines, N-methylaminoacetaldehyde (acetal 5-Methyloxazolo[3,2-a]pyridinium salts were shown to react with (methylamino)acetaldehyde dimethyl acetal leading to the formation of functionalized 5-aminoindolizines, which in turn are capable of closing the pyrimidine ring in acidic media forming aza[3.3.2] cyclazines.

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The structure of products of phenacylation and subsequent (re)cyclizations of 3-acetyl-4,6-dimethylpyridin-2(1H)-one according to X-ray structural analysis

Okul

Rybakov

Бабаев

2017

Chem Heterocycl Comp

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Transformations of Substituted Oxazolo- [3,2-a]Pyridines to 5,6-Disubstituted Indolizines: Synthesis And X-ray Structural Mapping

Cited by 7 publications

References 19 publications

Phenacylation of 6-Methyl-Beta-Nitropyridin-2-Ones and Further Heterocyclization of Products

Phenacylation of 6-Methyl-Beta-Nitropyridin-2-Ones and Further Heterocyclization of Products

Rearrangement of oxazolo[3,2-a]pyridines as an approach of synthesizing aza[3.3.2]cyclazines

The structure of products of phenacylation and subsequent (re)cyclizations of 3-acetyl-4,6-dimethylpyridin-2(1H)-one according to X-ray structural analysis

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