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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.  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
3.  3,4-Di­methyl­thieno[2,3-b]thio­phene-2,5-dicarbo­nitrile 
The asymmetric unit of the title compound, C10H6N2S2, contains two crystallographically independent but conformationally similar mol­ecules. The fused thio­phene ring cores are almost planar [maximum deviation = 0.027 (3) Å] with the thio­phene rings forming dihedral angles of 0.5 (4)° in one mol­ecule and 1.91 (4)° in the other. The crystal packing is stabilized only by van der Waals inter­actions.
doi:10.1107/S1600536813017960
PMCID: PMC3793767  PMID: 24109354
4.  Synthesis, reactions and biological activity of some new bis-heterocyclic ring compounds containing sulphur atom 
Background
The derivatives of thieno[2,3-b]thiophene belong to a significant category of heterocyclic compounds, which have shown a wide spectrum of medical and industrial application.
Results
A new building block with two electrophilic center of thieno[2,3-b]thiophene derivatives 2 has been reported by one-pot reaction of diketone derivative 1 with Br2/AcOH in excellent yield. A variety of heteroaromatics having bis(1H-imidazo[1,2a] benzimidazole), bis(1H-imidazo[1,2-b][1,2,4]triazole)-3-methyl-4-phenylthieno[2,3-b]thiophene derivatives, dioxazolo-, dithiazolo-, and 1H-imidazolo-3-methyl-4-phenylthieno[2,3-b]thiophene derivatives as well pyrrolo, thiazolo -3-methyl-4-phenylthieno[2,3-b]thiophene derivatives have been designed, synthesized, characterized, and evaluated for their biological activity. Compounds 3–9 showed good bioassay result. These new derivatives were evaluated for anti-cancer activity against PC-3 cell lines, in vitro antioxidant potential and β-glucuronidase and α-glucosidase inhibitory activities. Compound 3 (IC50 = 56.26 ± 3.18 μM) showed a potent DPPH radical scavenging antioxidant activity and found to be more active than standard N-acetylcystein (IC50 = 105.9 ± 1.1 μM). Compounds 8a (IC50 = 13.2 ± 0.34 μM) and 8b (IC50 = 14.1 ± 0.28 μM) found as potent inhibitor of α-glucusidase several fold more active than the standard acarbose (IC50 = 841 ± 1.73 μM). Most promising results were obtained in β-glucuronidase enzyme inhibition assay. Compounds 5 (IC50 = 0.13 ± 0.019 μM), 6 (IC50 = 19.9 ± 0.285 μM), 8a (IC50 = 1.2 ± 0.0785 μM) and 9 (IC50 = 0.003 ± 0.09 μM) showed a potent inhibition of β-glucuronidase. Compound 9 was found to be several hundred fold more active than standard D-Saccharic acid 1,4-lactone (IC50 = 45.75 ± 2.16 μM).
Conclusions
Synthesis, characterization, and in vitro biological activity of a series of thieno[2,3-b]thiophene have been investigated.
doi:10.1186/1752-153X-7-112
PMCID: PMC3728144  PMID: 23829861
Thienothiophene; Oxazole; Imidazole; Thiazole; Bisheterocycles; β-glucuronidase inhibition; α-glucosidase inhibition; DPPH radical scavenging activity; Ctotoxicity; Cancer cell line
5.  Ethyl 4-acetyl-5-anilino-3-methyl­thio­phene-2-carboxyl­ate 
In the title compound, C16H17NO3S, a thio­phene derivative with amino phenyl, acetyl, methyl and ethyl carboxyl susbtituents attached to a central thio­phene ring, the phenyl and thio­phene rings form a dihedral angle of 36.92 (9) Å. The mol­ecular conformation is stabilized by an intra­molecular N—H⋯O hydrogen bond, which forms an S(6) ring motif.
doi:10.1107/S160053681301547X
PMCID: PMC3772481  PMID: 24046624
6.  Dimethyl 2-(4-methyl­benzyl­idene)malonate 
In the mol­ecule of the title compound, C13H14O4, the benzene ring forms dihedral angles of 18.60 (7) and 81.36 (8)° with the two arms of the malonate moiety. The crystal structure features C—H⋯O inter­actions, which form chains running parallel to the b axis.
doi:10.1107/S1600536813012464
PMCID: PMC3685070  PMID: 23795089
7.  Synthesis of Thieno[2,3-b]thiophene Containing Bis-Heterocycles-Novel Pharmacophores 
Thioenethiophene derivatives represent an important class of compounds with diverse biological activities. We describe here the synthesis of a new series of thieno[2,3-b]thiophene containing bis-heterocyclic compounds 3–7. All the compounds were evaluated for their in vitro antioxidant potential, α-glucosidase and β-glucuronidase inhibiton and anticancer activity against PC-3 cell lines. Compounds 2b (IC50 = 1.3 ± 0.2 μM), 5a (IC50 = 2.3 ± 0.4 μM) and 5b (IC50 = 8.7 ± 0.1 μM) showed a potent inhibition of β-glucuronidase enzyme, more active than the standard d-saccharic acid 1,4-lactone (IC50 = 45.8 ± 2.5 μM). Compounds 5a (IC50 = 22.0 ± 0.3 μM) and 5b (IC50 = 58.4 ± 1.2 μM) were also found to be potent α-glucosidase inhibitors as compared to standard drug (acarbose, IC50 = 841 ± 1.7 μM).
doi:10.3390/ijms14035712
PMCID: PMC3634413  PMID: 23481634
thienothiophene; DPPH radical scavenging activity; β-glucuronidase inhibition; α-glucosidase inhibition; cytotoxicity; cancer cell lines
8.  (E)-Ethyl 2-anilino-5-[3-(dimethyl­amino)­acrylo­yl]-4-phenyl­thio­phene-3-carboxyl­ate 
In the title compound, C24H24N2O3S, the phenyl rings form dihedral angles of 55.65 (11) and 79.60 (11)° with the plane of the thio­phene ring. The mol­ecular conformation is stabilized by an intra­molecular N—H⋯O hydrogen bond, generating an S(6) ring motif. In the crystal, centrosymmetrically related mol­ecules are linked into dimers by two pairs of C—H⋯O inter­actions.
doi:10.1107/S1600536813003231
PMCID: PMC3588423  PMID: 23476543
9.  6-Hy­droxy­imino-5α-cholestane 
The title compound, C27H47NO, is a steroid derivative composed of a saturated carbon fused-ring framework with an alkyl side chain. Ring bond lengths have normal values with an average of 1.533 (2) Å, while the cholestane side chain shows an average bond length of 1.533 (2) Å. The three cyclohexane rings adopt chair conformations or close to chair conformations while the cyclopentane ring is twisted. The cholesterol side-chain is fully extended with a gauche–trans conformation of the terminal methyl groups. There are eight chiral centres in the molecule; the absolute configuration of these sites was determined from the structure presented. There are two molecules in the asymmetric unit; in one, the alkyl chain is disordered over two sets of sites [occupancy ratios of 0.50:0.50 and 0.67:0.33].
doi:10.1107/S1600536812040093
PMCID: PMC3470390  PMID: 23125803
10.  Synthesis and Characterization of Privileged Monodentate Phosphoramidite Ligands and Chiral Brønsted Acids Derived from d-Mannitol 
The synthesis of several novel chiral phosphoramidite ligands (L1–L8) with C2 symmetric, pseudo C2 symmetric secondary amines and chiral Brønsted acids 1a,b has been achieved. These chiral auxiliaries were obtained from commercially available d-mannitol, and secondary amines in moderate to excellent yields. Excellent diastereoselectivites of ten chiral auxiliaries were obtained. The chiral phosphoramidite ligands and chiral Brønsted acids were fully characterized by spectroscopic methods.
doi:10.3390/ijms13032727
PMCID: PMC3317684  PMID: 22489121
phosphoramidite; Brønsted acid; d-mannitol
11.  Synthesis and Antimicrobial Studies of Some Novel Bis-[1,3,4]thiadiazole and Bis-thiazole Pendant to Thieno[2,3-b]thiophene Moiety 
The synthetic utility of 3,3′-(3,4-dimethylthieno[2,3-b]thiophene-2,5-diyl)bis (3-oxopropanenitrile) (1) in the synthesis of some novel bis-[1,3,4-thiadiazole] 6a–g and bis-thiazole 10 and 13 derivatives with thieno[2,3-b]thiophene moiety is reported. Antimicrobial evaluation of some selected examples from the synthesized products was carried out and showed promising results.
doi:10.3390/ijms13033661
PMCID: PMC3317734  PMID: 22489174
thieno[2,3-b]thiophene; nucleophilic addition; hydrazonoyl halides; bis-thiadiazoles; bis-thiazoles; antimicrobial activity
12.  A Novel and Expedient Approach to New Thiazoles, Thiazolo[3,2-a]pyridines, Dihydrothiophenes, and Hydrazones Incorporating Thieno[2,3-b]thiophene Moiety 
This paper reports details about the synthesis of a series of novel functionalized symmetrical bis-heterocyclic compounds containing a thieno[2,3-b]thiophene motif. Bis-thiazole derivatives 2, 3a-c and thiazolo[3,2-a]pyridine derivatives 4a-c are achieved. The hitherto unknown dihydrothiophene derivatives 6a-d via bis-pyridimium salt 5 are obtained. Additionally, the novel hydrazonothieno[2,3-b]thiophene derivatives 10a-c are obtained via bis-tosylacetylthieno[2,3-b]thiophene derivative 9. All compounds are characterized by 1H-, 13C-NMR, GCMS, IR, and UV-vis spectrometry. These compounds represent a new class of sulfur and nitrogen containing heterocycles that should also be of interest as new materials.
doi:10.3390/ijms13045035
PMCID: PMC3344264  PMID: 22606028
thiazolo[3,2-a]pyridine; dihydrothiphene; thieno[2,3-b]thiophene; symmetrical bis-heterocycle
13.  A Practical Chemo-enzymatic Approach to Highly Enantio-Enriched 10-Ethyl-7,8-dihydro-γ-ionone Isomers: A Method for the Synthesis of 4,5-Didehydro-α-Ionone 
An efficient and convenient strategy for the enantioselective synthesis of enantiomerically enriched 10-ethyl-7,8-dihydro-γ-ionone isomers (R)-(+)-7, and (S)-(−)-7 are described utilizing a lipase mediated resolution protocol, and reductive elimination of the secondary allylic alcohol as the key step. The enantioselective and diastereoselective lipase kinetic acetylation of 4-hydroxy-γ-ionone derivatives 6a afforded the 4-acetyl-γ-ionone derivatives (−)-8, and the 4-hydrox-γ-ionone derivatives (+)-6a, which are suitable precursors of the desired products. Stereospecific palladium-mediated elimination of allylic acetate provides the target compounds with an excellent enantiomeric excess and yield. Additionally, the novel 4,5-didehydro-α-ionone 13 is obtained from readily prepared (2,6,6-trimethylcyclohexa-2,4-dien-1-yl) methanol 9. The structures of all newly synthesized compounds have been elucidated by 1H, 13C NMR, GC-MS, and IR spectrometry. These compounds represent a new class of odorants that may be of pivotal relevance in industrial perfumery.
doi:10.3390/ijms13055542
PMCID: PMC3382790  PMID: 22754314
timberol; ionone; bio-catalysis; lipase; asymmetric catalysis
14.  A Facile and Convenient Synthesis of some Novel Hydrazones, Schiff’s Base and Pyrazoles Incorporating Thieno[2,3-b]thiophenes 
A facile and convenient synthesis of some novel hydrazones, schiff’s base and pyrazoles from thieno[2,3-b]thiophene derivatives 1 have been achieved in high yields assisted by microwave and classical methods. The structures of all the title compounds have been elucidated by elemental analysis, IR, MS, 1H-NMR and 13C-NMR. Generally, these findings represent a new class of sulfur and nitrogen moieties that should also be of interest as new materials.
doi:10.3390/ijms12117824
PMCID: PMC3233441  PMID: 22174635
bicyclic compounds; hydrazone; thieno[2,3-b]thiophenes; heterocycles; schiff’s base

Results 1-14 (14)