New iminophosphorane-mediated synthesis of thieno[3′,2′:4,5]thieno[3,2-d]pyrimidin-4(3H)-ones and 5H-2,3-dithia-5,7-diaza-cyclopenta[c,d]indenes

Carbodiimide-based synthesis of N-heterocycles: moving from two classical reactive sites to chemical bond breaking/forming reaction

Carbodiimides are a unique class of heterocumulene compounds that display distinctive chemical properties. The rich chemistry of carbodiimides has drawn increasing attention from chemists in recent years and has made them exceedingly useful compounds in modern organic chemistry, especially in the synthesis of N-heterocycles. This review has outlined the extensive application of carbodiimides in the synthesis of N-heterocycles from the 1980s to today. A wide range of reactions for the synthesis of various types of N-heterocyclic systems (three-, four-, five-, six-, seven-, larger-membered and fused heterocycles) have been developed on the basis of carbodiimides and their derivatives.

An efficient synthesis of 3-alkyl-2-diversity-substituted benzofuro[3,2-d]pyrimidin-4(3H)-one derivatives

Benzofuro[3,2- d]pyrimidine derivatives are prepared using aza-Wittig reactions of iminophosphoranes with n-butyl isocyanate at 40–50 °C to give carbodiimide intermediates, which are reacted with nitrogen-oxygen-containing nucleophiles to give 3-alkyl-2-amino (aryloxy/alkoxy)-benzofuro[3,2- d]pyrimidin-4(3 H)-ones in satisfactory yields in the presence of a catalytic amount of sodium ethoxide or K2CO3. The iminophosphorane also reacts directly with excess carbon disulfide, followed by n-propylamine; further reaction with alkyl halides or halogenated aliphatic esters in the presence of anhydrous K2CO3 produces the corresponding 2-alkylthio-3-n-propyl-benzofuro[3,2- d]pyrimidin-4(3 H)-ones in good yields. Their structures of the products are confirmed by 1H NMR, 13C NMR, mass spectrometry, infrared and elemental analysis.

Synthesis of 2,5-asymmetrically substituted 3,4-diaminothieno[2,3-b]thiophenes by domino reaction

A convenient one pot synthesis of 2,5-asymmetrically substituted thieno[2,3-b]thiophenes is developed. The method is based on consecutive domino reactions (SN2 reaction → Thorpe-Ziegler reaction) using malononitrile and carbon disulfide as starting materials with the generation of potassium 2,2-dicyanoethene-1,1-bis(thiolate) in a solution. The high yield of the target thienothiophenes was achieved using the Ziegler dilution effect.

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.

Ethyl 3-bromo-4-cyano-5-[(2-eth-oxy-2-oxoeth-yl)sulfan-yl]thio-phene-2-carboxyl-ate

The title compound, C12H12BrNO4S2, was obtained by the Sandmeyer reaction from ethyl 3-amino-4-cyano-5-[(2-eth-oxy-2-oxoeth-yl)sulfan-yl]thio-phene-2-carboxyl-ate. The dihedral angle between the thiophene ring and linked CO2 ester group is 2.0 (5)°.

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, (1)H-NMR and (13)C-NMR. Generally, these findings represent a new class of sulfur and nitrogen moieties that should also be of interest as new materials.

6-Benzyl-2-[(triphenyl-λ-phosphanyl-idene)amino]-4,5,6,7-tetra-hydro-thieno[2,3-c]pyridine-3-carbonitrile

In the title compound, C(33)H(28)N(3)PS, the P atom has a distorted tetra-hedral PNC(3) environment, formed by the N atom and three aryl rings. No inter-molecular hydrogen-bonding inter-actions or π-π stacking inter-actions are present in the crystal structure.

Unexpected synthesis of indolo[1,2-c]quinazolines by a sequential Ugi 4CC-Staudinger-aza-Wittig-nucleophilic addition reaction

A new sequential Ugi-Staudinger-aza-Wittig-nucleophilic addition reaction was developed to construct indolo[1,2-c]quinazoline derivatives, starting from the easily accessible 2-azidobenzaldehyde, carboxylic acid, 2-acylaniline and isocyanide. It is noteworthy that this is the first report of the cyclization of the Ugi adduct to give a dihydroindole ring system with two quaternary carbon centers, via the nucleophilic addition reaction of the methine group to the carbonyl group.

Efficient synthesis and biological evaluation of some 2,4-diamino-furo[2,3-d]pyrimidine derivatives

The carbodiimides 2, obtained from aza-Wittig reactions of iminophosphorane 1 with aromatic isocyanates, reacted with ammonia to give ethyl 3,4-dihydro-6-methyl-4-oxo-2-arylamino-furo[2,3-d]pyrimidine-5-carboxylate 3. Further reaction of 3 with POCl(3) and various amines generated ethyl 4-alkylamino-2-arylamino-6-methyl-furo[2,3-d]pyrimidine-5-carboxylate 5 in good yields. Their structures were confirmed by (1)H NMR, EI-Ms, IR and elemental analysis. Compound 5b was further analyzed by single crystal X-ray diffraction. Compound 5 exhibited cytotoxicity against two lung cancer cell lines. For example, compound 5a showed the best inhibition activities against A459 with IC(50) 0.8μM.