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1.  Tandem Aldol-Michael reactions in aqueous diethylamine medium: a greener and efficient approach to dimedone-barbituric acid derivatives 
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.
doi:10.1186/1752-153X-8-9
PMCID: PMC3924718  PMID: 24485059
Tandem Aldol-Michael reactions; MCRs; Barbituric acid; Aqueous media; Green chemistry; Dimedone; Zwitterions
2.  (E)-1-(2,4-Di­nitro­phen­yl)-2-(3-eth­oxy-4-hy­droxy­benzyl­idene)hydrazine 
The mol­ecule of the title hydrazine derivative, C15H14N4O6, is essentially planar, the dihedral angle between the substituted benzene rings being 2.25 (9)°. The eth­oxy and hy­droxy groups are almost coplanar with their bound benzene ring [r.m.s. deviation = 0.0153 (2) Å for the ten non-H atoms]. Intra­molecular N—H⋯O and O—H⋯Oeth­oxy hydrogen bonds generate S(6) and S(5) ring motifs, respectively. In the crystal, mol­ecules are linked by O—H⋯Onitro hydrogen bonds into chains propagating in [010]. Weak aromatic π–π inter­actions, with centroid–centroid distances of 3.8192 (19) and 4.0491 (19) Å, are also observed.
doi:10.1107/S1600536813033989
PMCID: PMC3914112  PMID: 24527018
3.  (E)-2-[(2,4,6-Tri­meth­oxy­benzyl­idene)amino]­phenol1  
There are two independent mol­ecules in the asymmetric unit of the title compound, C16H17NO4, with similar conformations but some differences in their bond angles. Each mol­ecule adopts a trans configuration with respect to the methyl­idene C=N bond and is twisted with a dihedral angle between the two substituted benzene rings of 80.52 (7)° in one mol­ecule and 83.53 (7)° in the other. All meth­oxy groups are approximately coplanar with the attached benzene rings, with Cmeth­yl—O—C—C torsion angles ranging from −6.7 (2) to 5.07 (19)°. In the crystal, independent mol­ecules are linked together by O—H⋯N and O—H⋯O hydrogen bonds and a π–π inter­action [centroid–centroid distance of 3.6030 (9) Å], forming a dimer. The dimers are further linked by weak C—H⋯O inter­actions and another π–π inter­action [centroid–centroid distance of 3.9452 (9) Å] into layers lying parallel to the ab plane.
doi:10.1107/S1600536813032996
PMCID: PMC3914096  PMID: 24527001
4.  3-(Adamantan-1-yl)-4-ethyl-1-{[4-(2-meth­oxy­phen­yl)piperazin-1-yl]meth­yl}-1H-1,2,4-triazole-5(4H)-thione 
In the title compound, C26H37N5OS, the piperazine ring adopts a chair conformation. The triazole ring forms dihedral angles of 67.85 (9) and 59.41 (9)° with the piperazine and benzene rings, respectively, resulting in an approximate V-shaped conformation for the mol­ecule. An intra­molecular C—H⋯O hydrogen bond generates an S(6) ring motif. The crystal structure features C—H⋯π inter­actions, producing a two-dimensional supramolecular architecture.
doi:10.1107/S1600536813032789
PMCID: PMC3914072  PMID: 24526973
5.  2-[(E)-2-(4-Eth­oxy­phen­yl)ethen­yl]-1-methyl­quinolinium 4-fluoro­benzene­sulfonate 
In the structure of the title salt, C20H20NO+·C6H4FO3S−, the 4-(eth­oxy­phen­yl)ethenyl unit is disordered over two positions with a refined site-occupancy ratio of 0.610 (6):0.390 (6). The cation is nearly planar, the dihedral angle between the quinolinium and benzene rings being 6.7 (4) and 1.7 (7)° for the major and minor components, respectively. The eth­oxy group is essentially coplanar with the benzene ring [C—O—C—Cmethy = 177.1 (8) and 177.8 (12)° for the major and minor components, respectively]. In the crystal, cations and anions are linked into chains along the b-axis direction by C—H⋯Osulfon­yl weak inter­actions. These chains are further connected into sheets parallel to (001) by C—H⋯Osulfon­yl weak inter­actions. The chains are also stacked along the a axis through π–π inter­actions involving the quinolinium and benzene rings [centroid–centroid distances = 3.636 (5) Å for the major component and 3.800 (9) Å for the minor component]. C—H⋯π inter­actions are also present.
doi:10.1107/S1600536813032509
PMCID: PMC3914062  PMID: 24526963
6.  Tandem Aldol-Michael Reactions in Aqueous Diethylamine Medium: A Greener and Efficient Approach to Bis-Pyrimidine Derivatives 
A simple protocol, involving the green synthesis for the construction of novel bis-pyrimidine derivatives, 3a–i and 4a–e are accomplished by the aqueous diethylamine media promoted tandem Aldol-Michael reaction between two molecules of barbituric acid derivatives 1a,b with various aldehydes. This efficient synthetic protocol using an economic and environmentally friendly reaction media with versatility and shorter reaction time provides bis-pyrimidine derivatives with high yields (88%–99%).
doi:10.3390/ijms141223762
PMCID: PMC3876076  PMID: 24317435
tandem Aldol-Michael reactions; MCRs; barbituric acid; aqueous media; green chemistry
7.  2-[(E)-2-(4-Hy­droxy-3-meth­oxy­phen­yl)ethen­yl]-1-methylpyridinium 4-bromo­benzene­sulfonate monohydrate 
The title salt crystallized as the monohydrate C15H16NO2 +·C6H4BrSO3 −·H2O. The cation exists in an E conformation with respect to the ethynyl bond and is essentially planar, with a dihedral angle of 6.52 (14)° between the pyridinium and the benzene rings. The hy­droxy and meth­oxy substituents are coplanar with the benzene ring to which they are attached, with an r.m.s. deviation of 0.0116 (3) Å for the nine non-H atoms [Cmeth­yl—O—C—C torsion angle = −0.8 (4)°]. In the crystal, the cations and anions are stacked by π–π inter­actions, with centroid–centroid distances of 3.7818 (19) and 3.9004 (17) Å. The cations, anions and water mol­ecules are linked by O—H⋯O hydrogen bonds and weak C—H⋯O inter­actions, forming a three-dimensional network.
doi:10.1107/S1600536813031917
PMCID: PMC3885091  PMID: 24454267
8.  3-(Adamantan-1-yl)-1-[(4-benzyl­piperazin-1-yl)meth­yl]-4-ethyl-1H-1,2,4-triazole-5(4H)-thione 
In the title compound, C26H37N5S, the piperazine ring adopts a chair conformation with the exocyclic N—C bonds in pseudo-equatorial orientations. The piperazine ring (all atoms) subtends dihedral angles of 79.47 (9) and 73.07 (9)° with the triazole and benzene rings, respectively, resulting in an approximate U-shape for the mol­ecule. No significant inter­molecular inter­actions are observed in the crystal.
doi:10.1107/S1600536813031127
PMCID: PMC3885067  PMID: 24454243
9.  N-(Adamantan-1-yl)-1,2,3,4-tetra­hydro­iso­quinoline-2-carbo­thio­amide 
In the title compound, C20H26N2S, the N-containing six-membered ring adopts a boat conformation and the dihedral angle between the thio­carbamide group and the benzene ring is 49.67 (9)°. An intra­molecular C—H⋯S hydrogen bond generates an S(6) ring motif. The N—H group is sterically hindered and there are no significant inter­molecular inter­actions beyond van der Waals contacts.
doi:10.1107/S1600536813031516
PMCID: PMC3885068  PMID: 24454244
10.  6-(4-Amino­phen­yl)-2-meth­oxy-4-phenyl­nicotino­nitrile 
In the structure of the title nicotino­nitrile derivative, C19H15N3O, the pyridine ring makes dihedral angles of 11.50 (7) and 43.36 (8)° with the 4-amino­phenyl and phenyl rings, respectively, and the dihedral angle between the phenyl rings is 36.28°. In the crystal, mol­ecules are linked by N—H⋯N hydrogen bonds into wave-like sheets parallel to (10-2). These sheets are stacked by π–π inter­actions between the 4-amino­phenyl rings of adjacent sheets, with centroid–centroid distances of 3.7499 (9) Å. C—H⋯π inter­actions are also present.
doi:10.1107/S1600536813031437
PMCID: PMC3885069  PMID: 24454245
11.  Bis{4-[(E)-2-(1H-indol-3-yl)ethen­yl]-1-methyl­pyridinium} 4-chloro­benzene­sulfonate nitrate 
In the title mixed salt, 2C16H15N2 +·C6H4ClO3S−·NO3 −, one of the cations shows whole mol­ecule disorder over two sets of sites in a 0.711 (7):0.289 (7) ratio. The 4-chorobenzenesulfon­ate anion is also disordered over two orientations in a 0.503 (6):0.497 (6) ratio. The cations are close to planar, the dihedral angles between the pyridinium and indole rings being 1.48 (3)° in the ordered cation, and 5.62 (3) and 2.45 (3)°, respectively, for the major and minor components of the disordered cation. In the crystal, the cations are stacked in an anti­parallel manner approximately along the a-axis direction and linked with the anions via N—H⋯O hydrogen bonds and C—H⋯O inter­actions, generating a three-dimensional network. Weak C—H⋯π and π–π inter­actions [with centroid–centroid distances of 3.561 (2)–3.969 (7) Å] are also observed.
doi:10.1107/S1600536813030080
PMCID: PMC3885032  PMID: 24454207
12.  N-(4-Acetyl­phen­yl)-4-meth­oxy­benzene­sulfonamide 
The title compound, C15H15NO4S, was obtained by the condensation of 4-amino­aceto­phenone and 4-meth­oxy­benzene­sulfonyl chloride. The dihedral angle between the benzene rings is 86.56 (9)° and the mol­ecule has an approximate V-shaped conformation. The C atom of the meth­oxy group is roughly coplanar with its attached ring [deviation = 0.177 (3) Å], as is the methyl C atom of the acetyl group with its ring [deviation = 0.065 (2) Å]. An intra­molecular C—H⋯O inter­action generates an S(6) ring. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into [010] chains. Weak C—H⋯π inter­actions are also observed.
doi:10.1107/S1600536813029875
PMCID: PMC3885030  PMID: 24454205
13.  1-Methyl-4-[(E)-2-(3-hy­droxy-4-meth­oxy­phen­yl)ethen­yl]pyridinium 4-bromo­benzene­sulfonate monohydrate 
In the title hydrated salt, C15H16NO2 +·C6H4BrO3S−·H2O, the cation exists in an E conformation with respect to the ethenyl bond and is almost planar, with a dihedral angle of 2.62 (12)° between the planes of the pyridinium and benzene rings. The meth­oxy substituent deviates slightly from the plane of its attached benzene ring [Cmeth­yl—O—C—C torsion angle = −11.6 (6)°]. In the crystal, the cations, anion and water mol­ecules are linked together into chains along [010] by O—H⋯O hydrogen bonds and weak C—H⋯O inter­actions. There is a short Br⋯O contact [3.029 (2) Å]. The crystal structure also features C—H⋯π inter­actions involving the benzene ring of the anion.
doi:10.1107/S1600536813027244
PMCID: PMC3884297  PMID: 24454073
14.  Poly[μ5-(4-meth­oxy­benzene­sulfonato)-sodium] 
In the title complex, [Na(C7H7O4S)]n, the NaI ion is coord­inated in a slightly distorted penta­gonal-bipyramidal environment by seven O atoms [Na—O = 2.3198 (16)–2.5585 (17) Å]. The 4-methoxybenzenesulfonate anions act as bis-chelating and bridging ligands, forming a two-dimensional polymer parallel to (001), which is further linked into a three-dimensional network by weak C—H⋯O hydrogen bonds.
doi:10.1107/S1600536813025919
PMCID: PMC3790362  PMID: 24098184
15.  (E)-2-[4-(Di­ethyl­amino)­styr­yl]-1-methyl­quinolinium 4-fluoro­benzene­sulfonate monohydrate 
In the title hydrated molecular salt, C22H25N2 +·C6H4FO3S−·H2O, the cation displays whole mol­ecule disorder over two sets of sites in a 0.780 (5):0.220 (5) ratio. The quinolinium ring system is essentially planar, with r.m.s. deviations of 0.0162 and 0.0381 Å for the major and minor disorder components, respectively. The dihedral angles between the mean plane of the quinolinium ring system and the benzene ring are 5.1 (3) and 7.7 (11)°, respectively, for the major and minor components in the cation. In the crystal, cations, anions and water mol­ecules are linked into chains along [010] by O—H⋯O hydrogen bonds and are further connected into a three-dimensional network by weak C—H⋯O and C—H⋯F inter­actions. In addition, π–π inter­actions with centroid–centroid distances of 3.634 (3), 3.702 (5) and 3.838 (5) Å are observed.
doi:10.1107/S1600536813023532
PMCID: PMC3790381  PMID: 24098203
16.  6-Meth­oxy-4-(2,4,5-tri­meth­oxy­phen­yl)-2,2′-bi­pyridine-5-carbo­nitrile 
In the title 3-cyano­pyridine derivative, C21H19N3O4, the 3-cyano-substituted pyridine ring forms dihedral angles of 2.35 (5) and 41.60 (5)° with the unsubstituted pyridine and 2,4,5-trimeth­oxy-substituted benzene rings, respectively. The dihedral angle between the unsubstituted pyridine and benzene rings is 39.84 (5)°. The meth­oxy groups form Cmeth­yl—O—C—(C,N) torsion angles in the range 0.80 (15)–11.45 (15)°. In the crystal, mol­ecules related by 21 screw axes are linked by weak C—H⋯N hydrogen bonds along [010]. In addition, weak C—H⋯π inter­actions and π–π stacking inter­actions between pyridine rings, with a centroid–centroid distance of 3.6448 (6) Å, are observed.
doi:10.1107/S1600536813023891
PMCID: PMC3790375  PMID: 24098197
17.  Racemic 2′-hydroxy-4′,4′-dimethylpyran-1,5-dihydroxyxanthone monohydrate 
The title xanthone (systematic name: 3,6,11-trihy­droxy-1,1-dimethyl-2,3-di­hydro­chromeno[2,3-f]chromen-7-one monohydrate), known as pruniflorone N, crystallized as a monohydrate, C18H16O6·H2O. The three ring systems of the xanthone skeleton are approximately coplanar, with an r.m.s. deviation of 0.0270 (1) Å from the plane through the 14 non-H atoms. The O atoms of the two hy­droxy substituents on the benzene rings also lie close to this plane, with deviations of 0.019 (1) and 0.070 (1) Å. The 2′-hy­droxy-4′,4′-di­methyl­pyran ring is disordered over two positions with a 0.798 (3):0.202 (3) site-occupancy ratio. An intra­molecular O—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, the xanthone and water mol­ecules are linked into a three-dimensional network by O—H⋯O hydrogen bonds and weak C—H⋯O inter­actions. π–π inter­actions, with centroid–centroid distances of 3.5982 (7), 3.6081 (7) and 3.6456 (7) Å, are also observed.
doi:10.1107/S1600536813021223
PMCID: PMC3884455  PMID: 24427082
18.  3-(4-Amino­phen­yl)-5-(4-meth­oxy­phen­yl)-4,5-di­hydro-1H-pyrazole-1-carbo­thio­amide 
In the mol­ecule of title pyrazoline derivative, C17H18N4OS, the pyrazole ring adopts an envelope conformation with the flap atom, which bears the meth­oxy­phenyl substituent, displaced by 0.0750 (12) Å from the plane through the other ring atoms. The two substituted benzene rings make a dihedral angle of 70.59 (6)°. The meth­oxy group is twisted slightly with respect to the attached benzene ring [Cmeth­yl—O—C—C torsion angle = −8.84 (15)°]. An intra­molecular N—H⋯N hydrogen bond occurs. In the crystal, the pyrazoline mol­ecules are linked by N—H⋯O and N—H⋯S hydrogen bonds into zigzag layers parallel to the bc plane and stacked along the a axis by π–π inter­actions with centroid–centroid distances of 3.4690 (7) and 3.5792 (7) Å. C—H⋯π inter­actions are also present.
doi:10.1107/S1600536813018096
PMCID: PMC3793732  PMID: 24109319
19.  1-(2,4-Di­nitro­phen­yl)-2-[(E)-2,4,5-tri­meth­oxy­benzyl­idene]hydrazine 
The title compound, C16H16N4O7, is close to being planar, with a dihedral angle of 3.15 (11)° between the benzene rings. The meth­oxy groups at the ortho- and para-positions of the 2,4,5-tri­meth­oxy­phenyl group are almost coplanar with the ring [deviations of the C atoms = 0.017 (2) and −0.025 (2) Å, respectively], whereas the meta-meth­oxy group deviates slightly [C-atom displacement = 0.162 (2) Å]. Both the ortho- and para-nitro groups are close to being coplanar with their attached ring [dihedral angles = 7.81 (12) and 8.56 (11)°, respectively]. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds involving the same H atom as the intra­molecular bond generate R 2 2(12) loops. The dimers are linked by weak C—H⋯O inter­actions into sheets parallel to the (10-4) plane and the sheets are stacked by π–π inter­actions, with a centroid–centroid distance of 3.5974 (14) Å.
doi:10.1107/S1600536813018345
PMCID: PMC3793714  PMID: 24109301
20.  Methyl 3-[(6-nitro-4-oxo-3-phenyl-3,4-di­hydro­quinazolin-2-yl)sulfan­yl]propano­ate 
In the title compound, C18H15N3O5S, the approximately planar quinazoline ring system [maximum deviation = 0.097 (3) Å] forms a dihedral angle of 76.53 (19)° with the phenyl ring. The terminal -C(=O)—O—C group is disordered over two sets of sites with a site-occupancy ratio of 0.811 (17):0.189 (17). In the crystal, mol­ecules are linked via weak C—H⋯O hydrogen bonds into sheets parallel to the ac plane.
doi:10.1107/S1600536813016127
PMCID: PMC3770384  PMID: 24046669
21.  (2E)-1-(Pyridin-2-yl)-3-(2,4,5-tri­meth­oxy­phen­yl)prop-2-en-1-one 
The title heteroaryl chalcone derivative, C17H17NO4, is close to planar: the dihedral angle between the pyridine and benzene rings is 3.71 (11)° and the meth­oxy C atoms deviate from their attached ring by 0.046 (3), −0.044 (2) and 0.127 (3) Å. The disposition of the pyridine N atom and the carbonyl group is anti [N—C—C—O = −177.7 (2)°]. In the crystal, mol­ecules are linked by weak C—H⋯N and C—H⋯O inter­actions into (100) sheets and an aromatic π–π stacking inter­action between the pyridine and benzene ring, with a centroid–centroid separation of 3.7036 (14) Å also occurs.
doi:10.1107/S1600536813015821
PMCID: PMC3770358  PMID: 24046643
22.  (E)-1-(2-Amino­phen­yl)-3-(thio­phen-2-yl)prop-2-en-1-one 
The mol­ecule of the title heteroaryl chalcone derivative, C13H11NOS, exists in a trans-configuaration and is almost planar with a dihedral angle of 3.73 (8)° between the phenyl and thio­phene rings. An intra­molecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, two adjacent mol­ecules are linked into a dimer in an anti-parallel face-to-face manner by a pair of C—H⋯O inter­actions. Neighboring dimers are further linked into chains along the c-axis direction by N—H⋯N hydrogen bonds.
doi:10.1107/S1600536813014189
PMCID: PMC3772449  PMID: 24046592
23.  4-[(E)-(4-Eth­oxy­benzyl­idene)amino]­phenol 
The mol­ecule of the title compound, C15H15NO2, adopts a trans conformation with respect to the methyl­idene C=N bond and is twisted with a dihedral angle of 26.31 (5)° between the two substituted benzene rings. The eth­oxy group is almost coplanar with the bound benzene ring with a C—O—C—C torsion angle of −179.08 (9)°. In the crystal, mol­ecules are linked by O—H⋯N hydrogen bonds and weak C—H⋯O inter­actions into chains propagating in the [011] and [01-1] directions. C—H⋯π inter­actions are also present.
doi:10.1107/S1600536813012580
PMCID: PMC3685059  PMID: 23795078
24.  2-Amino-6-methyl-5-{5-[(naphthalen-2-yl­oxy)meth­yl]-1,3,4-oxadiazol-2-ylsulfan­yl}-4-(3-nitro­phen­yl)pyridine-3-carbonitrile 
The asymmetric unit of the title compound, C26H18N6O4S, contains two independent mol­ecules (A and B). The dihedral angles between the oxadiazole ring and naphthalene ring system are 42.59 (14) and 6.88 (14) Å in mol­ecules A and B, respectively. The dihedral angles between the pyridine and benzene rings in A and B are 65.53 (13 )and 87.67 (13) Å, respectively. In the crystal, mol­ecules A and B are linked through a pair of N—H⋯N hydrogen bonds involving one -NH2 group H atom and second pair of N—H⋯N hydrogen bonds involving the other -NH2 group H atom, forming an –ABAB– ribbon along [100] containing R 2 2(8) and R 2 2(12) ring motifs. These ribbons are further connected by weak C—H⋯N, C—H⋯O and C—H⋯π inter­actions, resulting in a three-dimensional network. The crystal studied was a non-merohedral twin with refined components 0.906 (1):0.094 (1).
doi:10.1107/S1600536813005837
PMCID: PMC3629525  PMID: 23634043
25.  Ethyl 2-[(2-oxo-2H-chromen-7-yl)­oxy]acetate 
In the title compound, C13H12O5, the mean plane of the 2H-chromene ring system (r.m.s deviation = 0.026 Å) forms a dihedral angle of 81.71 (6)° with the mean plane of ethyl 2-hy­droxy­acetate moiety (r.m.s deviation = 0.034 Å). In the crystal, C—H⋯O hydrogen bonds result in the formation of zigzag layers parallel to the bc plane.
doi:10.1107/S1600536813005539
PMCID: PMC3629532  PMID: 23634050

Results 1-25 (1302)