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Tandem Aldol-Michael reactions in aqueous diethylamine medium: a greener and efficient approach to dimedone-barbituric acid derivatives.

Barakat A, Al-Majid AM, Al-Ghamdi AM, Mabkhot YN, Rafiq Hussain Siddiqui M, Ghabbour HA, Fun HK - Chem Cent J (2014)

Bottom Line: From this view point, it is desirable to use water instead of organic solvents as a reaction medium, since water is safe, abundant and an environmentally benign solvent.The structure of 4a was further confirmed by single crystal X-ray diffraction.An environmentally benign Aldol-Michael protocol for the synthesis of dimedone-barbituric derivatives using aqueous diethylamine medium is achieved.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, College of Science, King Saud University, P,O, Box 2455, Riyadh 11451, Saudi Arabia. ambarakat@ksu.edu.sa.

ABSTRACT

Background: Green chemistry is a rapidly developing new field that provides us with a proactive avenue for the sustainable development of future science and technologies. Green chemistry uses highly efficient and environmentally benign synthetic protocols to deliver lifesaving medicines, accelerating lead optimization processes in drug discovery, with reduced unnecessary environmental impact. From this view point, it is desirable to use water instead of organic solvents as a reaction medium, since water is safe, abundant and an environmentally benign solvent.

Results: A convenient one-pot method for the efficient synthesis of the novel Zwitterion derivatives 4a-pvia a three-component condensation reaction of barbituric acid derivatives 1a,b, dimedone 2, and various aldehydes 3 in the presence of aqueous diethylamine media is described. This new approach is environmentally benign, with clean synthetic procedure, short reaction times and easy work-up procedure which proceeded smoothly to provide excellent yield (88-98%). The synthesized products were characterized by elemental analysis, IR, MS, NMR and CHN analysis. The structure of 4a was further confirmed by single crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group Pbca with α = 14.6669 (5) Å, b = 18.3084 (6) Å, c = 19.0294 (6) Å, α = 90°, β = 90°, = 90°, V = 5109.9 (3) Å3, and Z = 8. The molecules are packed in crystal structure by weak intermolecular C-H⋅ ⋅ ⋅O hydrogen bonding interactions.

Conclusions: An environmentally benign Aldol-Michael protocol for the synthesis of dimedone-barbituric derivatives using aqueous diethylamine medium is achieved.

No MeSH data available.


Related in: MedlinePlus

Crystal packing showing intermolecular C–H⋅O hydrogen bonds as dashed lines. 4a.
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Figure 4: Crystal packing showing intermolecular C–H⋅O hydrogen bonds as dashed lines. 4a.

Mentions: The X-ray zwitterion structure of 4a (Figure 3) was obtained using X-ray structure determination from a single crystal grown from CHCl3/Et2O as solvents. The structure shows interesting characteristics (Table 1). We were unable to determine the location of the C6 and C14 hydrogens by 1HNMR analysis. This is because the hydrogen from C6 dimedone, rather than hydrogen from C14 of the barbituric acid moiety, is removed by the basicity of diethylamine. This was confirmed by the X-ray structure because one hydrogen is on the diethylamine and the other is involved in hydrogen bonding interactions between both barbituric acid and dimedone moiety. The hydrogen-bonding interactions are listed in Table 2. Figure 4 depicts the packing of the molecules in the crystal structure. The crystal structure is stabilized by C–H⋅ ⋅ ⋅O hydrogen bonds into a three-dimensional framework structure. It is noteworthy to mention that 1HNMR have also shown a singlet signal at δ 15.28 ppm which can be assigned to the OH group which makes a hydrogen bond.


Tandem Aldol-Michael reactions in aqueous diethylamine medium: a greener and efficient approach to dimedone-barbituric acid derivatives.

Barakat A, Al-Majid AM, Al-Ghamdi AM, Mabkhot YN, Rafiq Hussain Siddiqui M, Ghabbour HA, Fun HK - Chem Cent J (2014)

Crystal packing showing intermolecular C–H⋅O hydrogen bonds as dashed lines. 4a.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3924718&req=5

Figure 4: Crystal packing showing intermolecular C–H⋅O hydrogen bonds as dashed lines. 4a.
Mentions: The X-ray zwitterion structure of 4a (Figure 3) was obtained using X-ray structure determination from a single crystal grown from CHCl3/Et2O as solvents. The structure shows interesting characteristics (Table 1). We were unable to determine the location of the C6 and C14 hydrogens by 1HNMR analysis. This is because the hydrogen from C6 dimedone, rather than hydrogen from C14 of the barbituric acid moiety, is removed by the basicity of diethylamine. This was confirmed by the X-ray structure because one hydrogen is on the diethylamine and the other is involved in hydrogen bonding interactions between both barbituric acid and dimedone moiety. The hydrogen-bonding interactions are listed in Table 2. Figure 4 depicts the packing of the molecules in the crystal structure. The crystal structure is stabilized by C–H⋅ ⋅ ⋅O hydrogen bonds into a three-dimensional framework structure. It is noteworthy to mention that 1HNMR have also shown a singlet signal at δ 15.28 ppm which can be assigned to the OH group which makes a hydrogen bond.

Bottom Line: From this view point, it is desirable to use water instead of organic solvents as a reaction medium, since water is safe, abundant and an environmentally benign solvent.The structure of 4a was further confirmed by single crystal X-ray diffraction.An environmentally benign Aldol-Michael protocol for the synthesis of dimedone-barbituric derivatives using aqueous diethylamine medium is achieved.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, College of Science, King Saud University, P,O, Box 2455, Riyadh 11451, Saudi Arabia. ambarakat@ksu.edu.sa.

ABSTRACT

Background: Green chemistry is a rapidly developing new field that provides us with a proactive avenue for the sustainable development of future science and technologies. Green chemistry uses highly efficient and environmentally benign synthetic protocols to deliver lifesaving medicines, accelerating lead optimization processes in drug discovery, with reduced unnecessary environmental impact. From this view point, it is desirable to use water instead of organic solvents as a reaction medium, since water is safe, abundant and an environmentally benign solvent.

Results: A convenient one-pot method for the efficient synthesis of the novel Zwitterion derivatives 4a-pvia a three-component condensation reaction of barbituric acid derivatives 1a,b, dimedone 2, and various aldehydes 3 in the presence of aqueous diethylamine media is described. This new approach is environmentally benign, with clean synthetic procedure, short reaction times and easy work-up procedure which proceeded smoothly to provide excellent yield (88-98%). The synthesized products were characterized by elemental analysis, IR, MS, NMR and CHN analysis. The structure of 4a was further confirmed by single crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group Pbca with α = 14.6669 (5) Å, b = 18.3084 (6) Å, c = 19.0294 (6) Å, α = 90°, β = 90°, = 90°, V = 5109.9 (3) Å3, and Z = 8. The molecules are packed in crystal structure by weak intermolecular C-H⋅ ⋅ ⋅O hydrogen bonding interactions.

Conclusions: An environmentally benign Aldol-Michael protocol for the synthesis of dimedone-barbituric derivatives using aqueous diethylamine medium is achieved.

No MeSH data available.


Related in: MedlinePlus