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1.  Crystal structure of 2-(1,3-dioxoindan-2-yl)iso­quinoline-1,3,4-trione 
In the title iso­quinoline-1,3,4-trione derivative, C18H9NO5, the five-membered ring of the indane fragment adopts an envelope conformation with the nitro­gen-substituted C atom being the flap. The planes of the indane benzene ring and the iso­quinoline-1,3,4-trione ring make a dihedral angle of 82.06 (6)°. In the crystal, mol­ecules are linked into chains extending along the bc plane via C—H⋯O hydrogen-bonding inter­actions, enclosing R 2 2(8) and R 2 2(10) loops. The chains are further connected by π–π stacking inter­ations, with centroid-to-centroid distances of 3.9050 (7) Å, forming layers parallel to the b axis.
doi:10.1107/S2056989014025997
PMCID: PMC4331915
crystal structure; iso­quinoline-1,3,4-trione derivative; synthesis; hydrogen bonding; pharmacological properties
2.  Crystal structure of cyclo­hexyl­ammonium thio­cyanate 
In the title salt, C6H11NH3 +·SCN−, the cyclo­hexyl­ammonium ring adopts a slightly distorted chair conformation. The ammonium group occupies an equatorial position to minimize 1,3 and 1,5 diaxial inter­actions. In the crystal, the components are linked by N—H⋯N and N—H⋯S hydrogen-bonding inter­actions, resulting in a three-dimensional network.
doi:10.1107/S2056989014027297
PMCID: PMC4331923
crystal structure; cyclo­hexyl­ammonium; distorted chair; hydrogen bonding
3.  Crystal structure of 2-(adamantan-1-yl)-5-(4-bromo­phen­yl)-1,3,4-oxa­diazole 
In the title mol­ecule, C18H19BrN2O, the benzene ring is inclined to the oxa­diazole ring by 10.44 (8)°. In the crystal, C—H⋯π inter­actions link the mol­ecules in a head-to-tail fashion, forming chains extending along the c-axis direction. The chains are further connected by π–π stacking inter­actions, with centroid–centroid distances of 3.6385 (7) Å, forming layers parallel to the bc plane.
doi:10.1107/S1600536814023861
PMCID: PMC4257436  PMID: 25553016
crystal structure; adamntane derivative; 1,3,4-oxa­diazole; C—H⋯π hydrogen bonds; π–π inter­actions
4.  Crystal structure of 6-chloro-5-iso­propyl­pyrimidine-2,4(1H,3H)-dione 
In the mol­ecule of the title compound, C7H9ClN2O2, the conformation is determined by intra­molecular C—H⋯O and C—H⋯Cl hydrogen bonds, which generate S(6) and S(5) ring motifs. The isopropyl group is almost perpendicular to the pyrimidine ring with torsion angles of −70.8 (3) and 56.0 (3)°. In the crystal, two inversion-related mol­ecules are linked via a pair of N—H⋯O hydrogen bonds into R 2 2(8) dimers; these dimers are connected into chains extending along the bc plane via an additional N—H⋯O hydrogen bond and weaker C—H⋯O hydrogen bonds. The crystal structure is further stabilized by a weak π–π inter­action [3.6465 (10) Å] between adjacent pyrimidine-dione rings arranged in a head-to-tail fashion, producing a three-dimensional network.
doi:10.1107/S1600536814021382
PMCID: PMC4257309  PMID: 25484791
crystal structure; pyrimidine-2,4-dione; hydrogen bonds; π–π inter­action
5.  Crystal structure of bis­{2-[(E)-(4-fluoro­benz­yl)imino­meth­yl]phenolato-κ2 N,O}nickel(II) 
In the square-planar [Ni(C14H11FNO)2] complex, weak C—H⋯F and C—H⋯π inter­actions play an important role in the mol­ecular self-assembly, resulting in the formation of 2D mol­ecular sheets which are stacked along the b axis.
The asymmetric unit of the title complex, [Ni(C14H11FNO)2], contains one-half of the mol­ecule with the NiII cation lying on an inversion centre coordinated by a bidentate Schiff base anion. The cationic NiII center is in a distorted square-planar coordination environment chelated by the imine N and phenolate O donor atoms of the two Schiff base ligands. The N and O donor atoms of the two ligands are mutually trans with Ni—N and Ni—O bond lengths of 1.9242 (10) and 1.8336 (9) Å, respectively. The fluoro­phenyl ring is almost orthogonal to the coordination plane and makes a dihedral angle of 82.98 (7)° with the phenolate ring. In the crystal, mol­ecules are linked into screw chains by weak C—H⋯F hydrogen bonds. Additional C—H⋯π contacts arrange the mol­ecules into sheets parallel to the ac plane.
doi:10.1107/S1600536814020546
PMCID: PMC4257226  PMID: 25484666
Crystal structure; Ni(II) complex; NO donors; Schiff base; anti­bacterial activity
6.  Crystal structure of bis­{2-[(E)-(4-meth­oxy­lbenz­yl)imino­meth­yl]phenolato-κ2 N,O 1}nickel(II) 
The NiII atom in the title compound shows a square-planar NiN2O2 coordination with the imine N and phenolate O atoms of the two Schiff base ligands. C—H⋯O and C—H⋯π interactions result in the formation of sheets of molecules parallel to the ac plane.
The asymmetric unit of the title compound, [Ni(C15H14NO2)2], comprises an NiII cation, lying on an inversion centre, and a Schiff base anion that acts as a bidentate ligand. The NiII cation is in a square-planar coordination environment binding to the imine N and phenolate O atoms of the two Schiff base ligands. The N- and O-donor atoms of the two ligands are mutually trans, with Ni—N and Ni—O bond lengths of 1.9191 (11) and 1.8407 (9) Å, respectively. The plane of the meth­oxy­benzene ring makes a dihedral angle of 84.92 (6)° with that of the phenolate ring. In the crystal, mol­ecules are linked into screw chains by weak C—H⋯O hydrogen bonds. Additional C—H⋯O hydrogen bonds, together with C—H⋯π contacts, arrange the mol­ecules into sheets parallel to the ac plane.
doi:10.1107/S160053681401650X
PMCID: PMC4158500  PMID: 25249867
crystal structure; nickel(II) complex; NO donors; Schiff base
7.  Bis{2-meth­oxy-6-[(E)-(4-methyl­benz­yl)imino­meth­yl]phenolato}palladium(II) chloro­form monosolvate 
In the title complex, [Pd(C16H16NO2)2]·CHCl3, the PdII cation lies on an inversion center. One Cl atom of the CHCl3 solvent mol­ecule lies on a twofold axis and the C—H group is disordered with equal occupancies about this axis with the other Cl atom in a general position with full occupancy. The PdII cation is four-coordinate and adopts a square-planar geometry via coordination of the imine N and phenolic O atoms of the two bidentate Schiff base anions. The N and O atoms of these ligands are mutually trans. The plane of the benzene ring makes a dihedral angle of 73.52 (10)° with that of the meth­oxy­phenolate ring. In the crystal, mol­ecules of the PdII complex are arranged into sheets parallel to the ac plane, and the chloro­form solvent mol­ecules are located in the inter­stitial areas between the complex mol­ecules. Weak inter­molecular C—H⋯O and C—H⋯π inter­actions stabilize the packing.
doi:10.1107/S1600536814015025
PMCID: PMC4158526  PMID: 25249876
crystal structure
8.  3-(Adamantan-1-yl)-4-benzyl-1H-1,2,4-triazole-5(4H)-thione 
The title compound, C19H23N3S, is a functionalized triazoline-3-thione derivative. The benzyl ring is almost normal to the planar 1,2,4-triazole ring (r.m.s. deviation = 0.007 Å) with a dihedral angle of 86.90 (7)°. In the crystal, molecules are linked by pairs of N—H⋯S hydrogen bonds, forming inversion dimers that enclose R 2 2(8) loops. The crystal packing is further stabilized by weak C—H⋯π inter­actions that link adjacent dimeric units into supra­molecular chains extending along the a-axis direction.
doi:10.1107/S1600536814013257
PMCID: PMC4120616  PMID: 25161557
9.  6-[(2-Methyl­phen­yl)sulfan­yl]-5-propyl­pyrimidine-2,4(1H,3H)-dione 
In the title pyrimidine-2,4-dione derivative, C14H16N2O2S, the dihedral angle between the six-membered rings is 77.81 (10)°. The mol­ecule is twisted about the Cp—S (p = pyrimidine) bond, with a C—S—C—N torsion angle of −59.01 (17)°. An intramolecular C—H⋯S hydrogen bond generates an S(5) ring motif. In the crystal, bifurcated acceptor N—H⋯O and C—H⋯O hydrogen bonds generate inversion-related dimers incorporating R 2 1(9) and R 2 2(8) loops. These dimers are connected into a chain extending along the a-axis direction by a second pair of inversion-related N—H⋯O hydrogen bonds, forming another R 2 2(8) loop. The crystal structure is further stabilized by weak inter­molecular C—H⋯π inter­actions, generating a three-dimensional network.
doi:10.1107/S1600536814013269
PMCID: PMC4120546  PMID: 25161558
10.  Investigation of supramolecular synthons and structural characterisation of aminopyridine-carboxylic acid derivatives 
Background
Co-crystal is a structurally homogeneous crystalline material that contains two or more neutral building blocks that are present in definite stoichiometric amounts. The main advantage of co-crystals is their ability to generate a variety of solid forms of a drug that have distinct physicochemical properties from the solid co-crystal components. In the present investigation, five co-crystals containing 2-amino-6-chloropyridine (AMPY) moiety were synthesized and characterized.
Results
The crystal structure of 2-amino-6-chloropyridine (AMPY) (I), and the robustness of pyridine-acid supramolecular synthon were discussed in four stoichiometry co-crystals of AMPY…BA (II), AMPY…2ABA (III), AMPY…3CLBA (IV) and AMPY…4NBA (V). The abbreviated designations used are benzoic acid (BA), 2-aminobenzoic acid (2ABA), 3-chlorobenzoic acid (3CLBA) and 4-nitrobenzoic acid (4NBA). All the crystalline materials have been characterized by 1HNMR, 13CNMR, IR, photoluminescence, TEM analysis and X-ray diffraction. The supramolecular assembly of each co-crystal is analyzed and discussed.
Conclusions
Extensive N---H · · · N/N---H · · · O/O---H · · · N hydrogen bonds are found in (I-V), featuring different supramolecular synthons. In the crystal structure, for compound (I), the 2-amino-6-chloropyridine molecules are linked together into centrosymmetric dimers by hydrogen bonds to form homosynthon, whereas for compounds (II-V), the carboxylic group of the respective acids (benzoic acid, 2-aminobenzoic acid, 3-chlorobenzoic acid and 4-nitrobenzoic acid) interacts with pyridine molecule in a linear fashion through a pair of N---H · · · O and O---H · · · N hydrogen bonds, generating cyclic hydrogen-bonded motifs with the graph-set notation
, to form heterosynthon. In compound (II), another intermolecular N---H · · · O hydrogen bonds further link these heterosynthons into zig-zag chains. Whereas in compounds (IV) and (V), these heterosynthons are centrosymmetrically paired via N---H · · · O hydrogen bonds and each forms a complementary DADA [D = donor and A = acceptor] array of quadruple hydrogen bonds, with graph-set notation, and .
Electronic supplementary material
The online version of this article (doi: 10.1186/1752-153X-8-31) contains supplementary material, which is available to authorized users.
doi:10.1186/1752-153X-8-31
PMCID: PMC4032391  PMID: 24887234
11.  Investigation of supramolecular synthons and structural characterisation of aminopyridine-carboxylic acid derivatives 
Background
Co-crystal is a structurally homogeneous crystalline material that contains two or more neutral building blocks that are present in definite stoichiometric amounts. The main advantage of co-crystals is their ability to generate a variety of solid forms of a drug that have distinct physicochemical properties from the solid co-crystal components. In the present investigation, five co-crystals containing 2-amino-6-chloropyridine (AMPY) moiety were synthesized and characterized.
Results
The crystal structure of 2-amino-6-chloropyridine (AMPY) (I), and the robustness of pyridine-acid supramolecular synthon were discussed in four stoichiometry co-crystals of AMPY…BA (II), AMPY…2ABA (III), AMPY…3CLBA (IV) and AMPY…4NBA (V). The abbreviated designations used are benzoic acid (BA), 2-aminobenzoic acid (2ABA), 3-chlorobenzoic acid (3CLBA) and 4-nitrobenzoic acid (4NBA). All the crystalline materials have been characterized by 1HNMR, 13CNMR, IR, photoluminescence, TEM analysis and X-ray diffraction. The supramolecular assembly of each co-crystal is analyzed and discussed.
Conclusions
Extensive N---H · · · N/N---H · · · O/O---H · · · N hydrogen bonds are found in (I-V), featuring different supramolecular synthons. In the crystal structure, for compound (I), the 2-amino-6-chloropyridine molecules are linked together into centrosymmetric dimers by hydrogen bonds to form homosynthon, whereas for compounds (II-V), the carboxylic group of the respective acids (benzoic acid, 2-aminobenzoic acid, 3-chlorobenzoic acid and 4-nitrobenzoic acid) interacts with pyridine molecule in a linear fashion through a pair of N---H · · · O and O---H · · · N hydrogen bonds, generating cyclic hydrogen-bonded motifs with the graph-set notation
R228
, to form heterosynthon. In compound (II), another intermolecular N---H · · · O hydrogen bonds further link these heterosynthons into zig-zag chains. Whereas in compounds (IV) and (V), these heterosynthons are centrosymmetrically paired via N---H · · · O hydrogen bonds and each forms a complementary DADA [D = donor and A = acceptor] array of quadruple hydrogen bonds, with graph-set notation R238, R228 and R238.
doi:10.1186/1752-153X-8-31
PMCID: PMC4032391  PMID: 24887234
13.  Microwave irradiation: synthesis and characterization of α-ketoamide and bis (α-ketoamide) derivatives via the ring opening of N-acetylisatin 
Background
The carbonyl group at position 2 of N-acetylisatin behaves as an amide which is more susceptible to nucleophilic attack via ring-opening in the presence of nucleophiles. Because of this behavior, in the present work we describe the microwave synthesis of a series of α-ketoamide and bis-(α-ketoamide) derivatives via the facile ring-opening of N-acylisatin with different amines and diamines. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the ester derivatives with piperidine and morpholine afforded the same α-ketoamide derivatives obtained from direct aminolysis of N-acylisatin. The structures of the synthesized compounds were confirmed by FT-IR, NMR, X-ray and elemental analysis.
Results
Reaction of N-acetylisatin and N-propoionylsatin with different amines and diamines afforded a series of α-ketoamide and bis-(α-ketoamide) derivatives respectively via the ring opening of N-acylisatins. The reaction was performed under conventional condition as well as microwave irradiation. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives in excellent yields and purities as observed from their spectral data. A plausible mechanism involves nucleophilic attack by methanol at C2 carbonyl carbon of N-acetylisatin and subsequent ring opening to generate the α-ketoester. Aminolysis of α-ketoester with amine afforded the same α-ketoamide which is obtained by direct aminolysis of N-acylisatin. The IR, NMR spectra, microanalyses, and single crystal X-ray diffraction confirmed the structures of the synthesized compounds.
Conclusions
In conclusion, we have demonstrated that microwave irradiation could be employed efficiently for the synthesis of biologically important α-ketoamide and bis-(α-ketoamide) derivatives. The microwave irradiation has more advantageous over the classical method with regard to reaction time, solvent quantity, and product yield. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the methyl ester derivatives with amine under microwave irradiation afford the same α-ketoamide derivatives as obtained from direct aminolysis of N-acylisatins.
Electronic supplementary material
The online version of this article (doi:10.1186/1752-153X-8-27) contains supplementary material, which is available to authorized users.
doi:10.1186/1752-153X-8-27
PMCID: PMC4021159  PMID: 24839460
N-acetylisatin; N-propionylisatin; Microwave irradiation; α-ketoamide; bis- α-ketoamide; X-ray crystallography
14.  Microwave irradiation: synthesis and characterization of α-ketoamide and bis (α-ketoamide) derivatives via the ring opening of N-acetylisatin 
Background
The carbonyl group at position 2 of N-acetylisatin behaves as an amide which is more susceptible to nucleophilic attack via ring-opening in the presence of nucleophiles. Because of this behavior, in the present work we describe the microwave synthesis of a series of α-ketoamide and bis-(α-ketoamide) derivatives via the facile ring-opening of N-acylisatin with different amines and diamines. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the ester derivatives with piperidine and morpholine afforded the same α-ketoamide derivatives obtained from direct aminolysis of N-acylisatin. The structures of the synthesized compounds were confirmed by FT-IR, NMR, X-ray and elemental analysis.
Results
Reaction of N-acetylisatin and N-propoionylsatin with different amines and diamines afforded a series of α-ketoamide and bis-(α-ketoamide) derivatives respectively via the ring opening of N-acylisatins. The reaction was performed under conventional condition as well as microwave irradiation. The microwave irradiation afforded the product in less reaction time, higher yield and purity. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives in excellent yields and purities as observed from their spectral data. A plausible mechanism involves nucleophilic attack by methanol at C2 carbonyl carbon of N-acetylisatin and subsequent ring opening to generate the α-ketoester. Aminolysis of α-ketoester with amine afforded the same α-ketoamide which is obtained by direct aminolysis of N-acylisatin. The IR, NMR spectra, microanalyses, and single crystal X-ray diffraction confirmed the structures of the synthesized compounds.
Conclusions
In conclusion, we have demonstrated that microwave irradiation could be employed efficiently for the synthesis of biologically important α-ketoamide and bis-(α-ketoamide) derivatives. The microwave irradiation has more advantageous over the classical method with regard to reaction time, solvent quantity, and product yield. Reaction of N-acylisatin with methanol under microwave irradiation afforded the α-phenylglyoxyl methyl ester derivatives with excellent yields and purities. Aminolysis of the methyl ester derivatives with amine under microwave irradiation afford the same α-ketoamide derivatives as obtained from direct aminolysis of N-acylisatins.
doi:10.1186/1752-153X-8-27
PMCID: PMC4021159  PMID: 24839460
N-acetylisatin; N-propionylisatin; Microwave irradiation; α-ketoamide; bis- α-ketoamide; X-ray crystallography
15.  (1E,4E)-1,5-Bis[4-(di­ethyl­amino)­phen­yl]penta-1,4-dien-3-one 
There are two crystallograpically independent mol­ecules in the asymmetric unit of the title bis­chalcone derivative, C25H32N2O. Both mol­ecules are twisted with a dihedral angle between the two substituted benzene rings of 11.19 (16)° in one mol­ecule and 14.40 (15)° in the other. The central penta-1,4-dien-3-one fragments make dihedral angles of 8.49 (17) and 4.26 (17)° with the two adjacent benzene rings in one mol­ecule, whereas the corresponding values are 8.42 (16) and 6.18 (16)° in the other. In the crystal, mol­ecules are arranged into chains along the c-axis direction. Adjacent chains are inter-linked by weak inter­molecular C—H⋯O inter­actions. The crystal is further stabilized by C—H⋯π inter­actions.
doi:10.1107/S1600536814008356
PMCID: PMC4011286  PMID: 24860388
16.  2,2′-[2,4-Bis(naphthalen-1-yl)cyclo­butane-1,3-di­yl]bis­(1-methyl­pyridinium) bis­(4-chloro­benzene­sulfonate): thermal-induced [2 + 2] cyclo­addition reaction of a heterostilbene 
The asymmetric unit of the title salt, C36H32N2 2+·2C6H4ClO3S−, consists of one anion and one half-cation, the other half being generated by inversion symmetry. The dihedral angle between the pyridinium ring and the napthalene ring system in the asymmetric unit is 42.86 (6)°. In the crystal, cations and anions are linked by weak C—H⋯O inter­actions into chains along [010]. Adjacent chains are further arranged in an anti­parallel manner into sheets parallel to the bc plane. π–π inter­actions are observed involving the cations, with centroid–centroid distances of 3.7664 (8) and 3.8553 (8) Å.
doi:10.1107/S160053681400645X
PMCID: PMC4011255  PMID: 24860326
17.  Trichodermaerin: a diterpene lactone from Trichoderma asperellum  
The title compound, C20H28O3, known as ‘trichodermaerin’ [systematic name: (4E)-4,9,15,16,16-penta­methyl-6-oxa­tetra­cyclo­[10.3.1.01,10.05,9]hexa­dec-4-ene-7,13-dione], is a diterpene lactone which was isolated from Trichoderma asperellum. The structure has a tetra­cycic 6–5–7–5 ring system, with the cyclo­hexa­none ring adopting a twisted half-chair conformation and the cyclo­pentane ring adopting a half-chair conformation, whereas the cyclo­heptene and tetra­hydro­furan­anone rings are in chair and envelope (with the methyl-substituted C atom as the flap) conformations, respectively. The three-dimensional architecture is stabilized by C—H⋯O inter­actions.
doi:10.1107/S1600536814004632
PMCID: PMC3998585  PMID: 24826124
18.  (E)-2-[4-(Di­ethyl­amino)­styr­yl]-1-methyl­quinolin-1-ium 4-chloro­benzene­sulfonate monohydrate 
The asymmetric unit of the title hydrated salt, C22H25N2 +·C6H4ClO3S−·H2O, comprises two 2-[4-(di­ethyl­amino)­styr­yl]-1-methyl­quinolin-1-ium cations, two 4-chloro­benzene­sul­fon­ate anions and two solvent water mol­ecules. One ethyl group of both cations displays disorder over two positions in a 0.659 (2):0.341 (2) ratio in one mol­ecule and in a 0.501 (2):0.499 (2) ratio in the other. The sulfonate group of one anion is also disordered over two positions in a 0.893 (7):0.107 (7) ratio. The dihedral angle between the mean plane of the quinolinium ring system and that of benzene ring is 10.57 (18)° in one cation and 14.4 (2)° in the other. In the crystal, cations, anions and water mol­ecules are linked into chains along the [010] direction by O—H⋯Osulfonate hydrogen bonds, together with weak C—H⋯Osulfonate and C—H⋯Cl inter­actions. The cations are stacked by π–π inter­actions, with centroid–centroid distances in the range 3.675 (2)–4.162 (3) Å.
doi:10.1107/S1600536814004577
PMCID: PMC3998564  PMID: 24826116
19.  Cyclo­hexyl­ammonium nitrate 
In the title salt, C6H14N+·NO3 −, the cyclo­hexyl ring adopts a chair conformation. The ammonium group occupies an equatorial position and the crystal struture is stabilized by inter­molecular N—H⋯O hydrogen-bonding inter­actions, resulting in a three-dimensional network.
doi:10.1107/S1600536814002244
PMCID: PMC3998418  PMID: 24764971
20.  4-(2-Meth­oxy­phen­yl)piperazin-1-ium 6-chloro-5-isopropyl-2,4-dioxopyrimidin-1-ide 
In the cation of the title salt, C11H17N2O+·C7H8ClN2O2 −, the piperazine ring adopts a distorted chair conformation and contains a positively charged N atom with quaternary character. Its mean plane makes a dihedral angle of 42.36 (8)° with the phenyl ring of its 2-meth­oxy­phenyl substituent. The 2,4-dioxopyrimidin-1-ide anion is generated by deprotonation of the N atom at the 1-position of the pyrimidine­dione ring. Intra­molecular C—H⋯O hydrogen bonds generate S(6) ring motifs in both the cation and the anion. In the crystal, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds are also observed, resulting in a two-dimensional network parallel to the ab plane. The crystal stability is further consolidated by weak C—H⋯π inter­actions.
doi:10.1107/S1600536814002256
PMCID: PMC3998442  PMID: 24764966
21.  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
22.  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
23.  5-Propyl-6-(p-tolyl­sulfan­yl)pyrimidine-2,4(1H,3H)-dione 
In the title pymiridine-2,4-dione derivative, C14H16N2O2S, the dihedral angle between the six-membered rings is 66.69 (10)°. The mol­ecule is twisted about the Cp—S (p = pyrimidine) bond, with a C—S—C—N torsion angle of −19.57 (16)°. In the crystal, adjacent mol­ecules form inversion dimers through pairs of strong N—H⋯O hydrogen bonds, generating an R 2 2(8) ring motif. The dimers are connected into chains extending along the c-axis direction through additional N—H⋯O hydrogen bonds.
doi:10.1107/S1600536814000749
PMCID: PMC3998333  PMID: 24764894
24.  1-(2,4-Di­nitro­phen­yl)-2-[(E)-(3,4,5-tri­meth­oxy­benzyl­idene)]hydrazine 
Mol­ecules of the title compound, C16H16N4O7, are not planar with a dihedral angle of 5.50 (11)° between the substituted benzene rings. The two meta-meth­oxy groups of the 3,4,5-tri­meth­oxy­benzene moiety lie in the plane of the attached ring [Cmeth­yl–O–C–C torsion angles −0.1 (4)° and −3.7 (3)°] while the para-meth­oxy substituent lies out of the plane [Cmeth­yl—O—C—C, −86.0 (3)°]. An intra­molecular N—H⋯O hydrogen bond involving the 2-nitro substituent generates an S(6) ring motif. In the crystal structure, mol­ecules are linked by weak C—H⋯O inter­actions into screw chains, that are arranged into a sheet parallel to the bc plane. These sheets are connected by π–π stacking inter­actions between the nitro and meth­oxy substituted aromatic rings with a centroid–centroid separation of 3.9420 (13) Å. C—H⋯π contacts further stabilize the two-dimensional network.
doi:10.1107/S1600536814001238
PMCID: PMC3998339  PMID: 24764900
25.  (E)-4-Meth­oxy-N′-(2,4,5-tri­meth­oxy­benzyl­idene)benzohydrazide hemihydrate 
The title compound crystallizes as a hemihydrate, C18H20N2O5·0.5H2O. The mol­ecule exists in an E conformation with respect to the C=N imine bond. The 4-meth­oxy­phenyl unit is disordered over two sets of sites with a refined occupancy ratio of 0.54 (2):0.46 (2). The dihedral angles between the benzene rings are 29.20 (9) and 26.59 (9)°, respectively, for the major and minor components of the 4-meth­oxy-substituted ring. All meth­oxy substituents lie close to the plane of the attached benzene rings [the Cmeth­yl—O—C—C torsion angles range from −4.0 (12) to 3.9 (2)°]. In the crystal, the components are linked into chains propagating along [001] via N—H⋯O and O—H⋯O hydrogen bonds and weak C—H⋯O inter­actions.
doi:10.1107/S1600536814000531
PMCID: PMC3998312  PMID: 24764873

Results 1-25 (1325)