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Synthesis of fused uracils: pyrano[2,3-d]pyrimidines and 1,4-bis(pyrano[2,3-d]pyrimidinyl)benzenes by domino Knoevenagel/Diels-Alder reactions.

Pałasz A - Monatsh. Chem. (2012)

Bottom Line: Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5'-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excellent yields (75-88 %).All reactions were carried out without catalyst at room temperature.The reactions of malononitrile with Knoevenagel condensation products of barbituric acids and heteroaromatic aldehydes or terephthalaldehyde were examined and did not provide corresponding pyranopyrimidines. .

View Article: PubMed Central - PubMed

Affiliation: Department of Organic Chemistry, Jagiellonian University, Kraków, Poland.

ABSTRACT

Abstract: Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5'-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excellent yields (75-88 %). Syntheses were realized by Knoevenagel condensation and HDA reaction in four different reaction conditions: Knoevenagel condensation in water and Diels-Alder reaction in methylene chloride solution, Knoevenagel condensation in water and Diels-Alder reaction without solvent, three-component one-pot reaction in methylene chloride solution, or three-component one-pot reaction in water. All reactions were carried out without catalyst at room temperature. The reactions of malononitrile with Knoevenagel condensation products of barbituric acids and heteroaromatic aldehydes or terephthalaldehyde were examined and did not provide corresponding pyranopyrimidines.

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Mentions: At the end of the study, the reaction procedures E–H presented above were examined for acid 1a, terephthalaldehyde 2d, and malononitrile 9. The reaction of 1a with aldehyde 2d in water at room temperature gave condensation product 3d with almost stoichiometric yield after 1 h. When compound 3d was heated with malononitrile 9 in water for 1 h (method E, Scheme 4) or in acetonitrile in the presence of piperidine for 3 h (method F, Scheme 4), the expected compound 13 was not obtained.Scheme 4


Synthesis of fused uracils: pyrano[2,3-d]pyrimidines and 1,4-bis(pyrano[2,3-d]pyrimidinyl)benzenes by domino Knoevenagel/Diels-Alder reactions.

Pałasz A - Monatsh. Chem. (2012)

 
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4495049&req=5

Sch4:  
Mentions: At the end of the study, the reaction procedures E–H presented above were examined for acid 1a, terephthalaldehyde 2d, and malononitrile 9. The reaction of 1a with aldehyde 2d in water at room temperature gave condensation product 3d with almost stoichiometric yield after 1 h. When compound 3d was heated with malononitrile 9 in water for 1 h (method E, Scheme 4) or in acetonitrile in the presence of piperidine for 3 h (method F, Scheme 4), the expected compound 13 was not obtained.Scheme 4

Bottom Line: Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5'-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excellent yields (75-88 %).All reactions were carried out without catalyst at room temperature.The reactions of malononitrile with Knoevenagel condensation products of barbituric acids and heteroaromatic aldehydes or terephthalaldehyde were examined and did not provide corresponding pyranopyrimidines. .

View Article: PubMed Central - PubMed

Affiliation: Department of Organic Chemistry, Jagiellonian University, Kraków, Poland.

ABSTRACT

Abstract: Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5'-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excellent yields (75-88 %). Syntheses were realized by Knoevenagel condensation and HDA reaction in four different reaction conditions: Knoevenagel condensation in water and Diels-Alder reaction in methylene chloride solution, Knoevenagel condensation in water and Diels-Alder reaction without solvent, three-component one-pot reaction in methylene chloride solution, or three-component one-pot reaction in water. All reactions were carried out without catalyst at room temperature. The reactions of malononitrile with Knoevenagel condensation products of barbituric acids and heteroaromatic aldehydes or terephthalaldehyde were examined and did not provide corresponding pyranopyrimidines.

Graphical abstract: .

No MeSH data available.


Related in: MedlinePlus