Thiophene, as a member of the group of five‐membered heterocycles containing one heteroatom, is one of the simplest heterocyclic systems. Many synthetic strategies allow the accurate positioning of ...various functionalities onto the thiophene ring. This review provides a comprehensive, systematic and detailed account of the developments in the field of antimicrobial compounds featuring at least one thiophene ring in their structure, over the last decade.
Thiophene, a five‐membered ring containing one heteroatom, is one of the simplest heterocyclic systems. There are many synthetic strategies allowing the accurate positioning of various functionalities onto the thiophene ring. This review provides a systematic account of the developments over the last decade in the field of antimicrobial compounds featuring at least one thiophene ring in their structure.
The current report provides an overview of the rapidly developing class of pyrazolines having a benzothiazole moiety at N
1
. The synthetic approaches (mainly through the 3 + 2 cyclo-condensation of ...chalcone analogs with 2-hydrazinobenzothiazole) toward these particular pyrazolines, along with their chemical transformation to pyrazoles through oxidation are outlined. The photophysical properties (absorption and emission spectra) along with their applications as fluorescent chemosensors have been summarized. 1-(2-Benzothiazolyl)pyrazolines exhibit significant fluorescence quenching mostly in the presence of transition metal ions, such as Fe
3+
, Cu
2+
, Hg
2+
, Zn
2+
, or Ni
2+
, but also toward Al
3+
, thus enabling the selective detection of these analytes. In addition, examples of 1-(2-benzothiazolyl)pyrazolines acting as chemosensors for anions such as S
2−
or F
−
are also available. Comprehensive examination of the biological properties of 1-(2-benzothiazolyl)pyrazolines shows that members of this class possess either broad or selective significant antimicrobial activity, along with tuberculostatic activity and cytotoxicity that is sometimes better than that of positive controls. The antidiabetic, anti-inflammatory, anthelmintic, and antimalarial activity of these compounds, along with their potential for inhibition of enzymes such as carbonic anhydrase or acetylcholinesterase have been briefly explored.
Graphical abstract
The biological activity of Mannich bases, a structurally heterogeneous class of chemical compounds that are generated from various substrates through the introduction of an aminomethyl function by ...means of the Mannich reaction, is surveyed, with emphasis on the relationship between structure and biological activity. The review covers extensively the literature reports that have disclosed Mannich bases as anticancer and cytotoxic agents, or compounds with potential antibacterial and antifungal activity in the last decade. The most relevant studies on the activity of Mannich bases as antimycobacterial agents, antimalarials, or antiviral candidates have been included as well. The review contains also a thorough coverage of anticonvulsant, anti-inflammatory, analgesic and antioxidant activities of Mannich bases. In addition, several minor biological activities of Mannich bases, such as their ability to regulate blood pressure or inhibit platelet aggregation, their antiparasitic and anti-ulcer effects, as well as their use as agents for the treatment of mental disorders have been presented. The review gives in the end a brief overview of the potential of Mannich bases as inhibitors of various enzymes or ligands for several receptors.
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•Biological activities of structurally diverse Mannich bases are being reviewed.•Anticancer, antibacterial and antifungal activities are presented extensively.•Antimycobacterial, antimalarial and antiviral activities of Mannich bases are also covered.•Minor biological activities of Mannich bases are also summarized.•An overview of Mannich bases as inhibitors of enzymes and ligands for receptors is provided.
Fluorescence detection is currently one of the commonly used techniques worldwide. Through this work, the preparation and optical properties of an interesting composite material are discussed. It is ...shown that encapsulating cobalt spinel ferrite (CoFe2O4), obtained by the sol-gel autocombustion method, into polydiphenyl-co-methyl(H)silane matrix leads to fluoromagnetic particles (PSCo) with intriguing optical properties. Transmission electron microscopy, combined with energy-dispersive X-ray analysis, showed 500 nm large spherical structures containing a core (around 400 nm in diameter) composed of magnetic ferrite particles, surrounded by a thin layer of semiconductive fluorescent polymer. The as-obtained material exhibited ferrimagnetic properties. The FTIR spectrum confirmed that the Si-H functionality of the polysilane was preserved. UV spectroscopy combined with molecular modeling studies indicated that the magnetic core had a strong influence on the intramolecular electron transitions characteristic of the σ-conjugated polysilane. Further analysis by steady-state fluorescence spectroscopy revealed that the internal magnetic field strongly enhances the polysilane emission. This property will be further investigated in the future in order to develop new detection devices.
Compounds with a pyrazoline scaffold are useful as sensors for fluorescence detection of different types of analytes. Recovery of a pyrazoline-based sensor with a view to use it recurrently would be ...more facile when the sensing molecule is attached to a solid support. A reaction sequence has been designed to synthesize two benzaldehyde-pyrazoline hybrids as examples of a hitherto unknown type of compounds to be employed for the potential derivatization of polymers containing primary amino groups through azomethine formation. All intermediates, including the fairly unstable N1 -unsubstituted pyrazolines, along with the target compounds have been structurally characterized, with an emphasis on their particular NMR features. Examination of the photophysical properties of these benzaldehyde-pyrazoline hybrids showed that, despite the shortening of the extended N1-N2-C3 conjugated system common to 1,3,5-triarylpyrazolines through the replacement of the aryl at N1 by an aryloxyacetyl moiety, the novel compounds exhibit emission maxima at approximately 350 nm. Moreover, the introduction of a moderately electron-withdrawing substituent such as chlorine in the phenyl at C3 of pyrazoline leads to an amplification of fluorescence intensity.
Benzimidazole, benzimidazoles diversely substituted at position 2, and 5,6-dimethylbenzimidazole have been alkylated at
N
1
with ketonic Mannich bases derived from acetophenones, acetylnaphthalenes, ...2-acetylthiophene and 1-tetralone to afford a series of novel 1-(3-oxopropyl)benzimidazoles. The reduction of these transamination products with NaBH
4
in methanol produced the corresponding 1-(3-hydroxypropyl)benzimidazoles in excellent yields.
Fast, easy, and scalable methodologies for the synthesis of
unsymmetrically-substituted secondary amines containing naphthalene, indole,
pyridine and imidazole moieties through reductive amination ...were explored.
The investigated operating procedures were successful on a 50- to 30-mmole
scale, and presented a high potential for upscaling.
nema
1-(5-Bromobenzofuran-2-yl)ethan-1-one has been employed as substrate in a direct Mannich reaction with common secondary amines to generate several ß-aminoketones hydrochlorides. Alkylation of S- and ...N-nucleophiles (4-chlorothiophenol, piperazine, sulfanilamide, 3,5-dimethylpyrazole) with the dimethylamine-containing ß-aminoketone derived from the aforementioned substrate has also been investigated. Reaction of the same ketonic Mannich base with phenylhydrazine afforded the corresponding 1,3-disubstituted pyrazoline, whose UV-Vis absorption has been measured in dimethylsulfoxide, toluene and chloroform at room temperature to give similar spectra having a maximum at approximately 390 nm. The fluorescence spectrum of this pyrazoline in toluene is more intense and blue-shifted compared to its emission spectrum in dimethylsulfoxide.
Four novel ditopic ligands that have a pyrazole ring in their central unit and are useful for the generation of coordination polymers have been synthesized. Two of these ditopic ligands present two ...carboxylate functions as coordinating groups, while the other two are hybrid ligands having only one carboxylate function and either tetrazolate or imidazole as the remaining coordination site. The ligands have been obtained through a multi-step reaction sequence that begins with the Claisen condensation of either 4-acetylbenzonitrile or 4-(1
H
-imidazol-1-yl)acetophenone with diethyl oxalate and has the Knorr pyrazole ring closure as its key step. Subsequently, the tetrazolate in one of the ligands is constructed through a 3 + 2 cycloaddition of azide anion to the cyano group, while hydrolysis of the ester and the cyano substituents generates the carboxylate function(s). The structure of the intermediates and of the target ligands has been investigated by solution NMR, special attention being given to keto–enol and pyrazole tautomerism when present. The structure of two ligands and a key intermediate has also been established by single-crystal X-ray diffraction.
Several novel 2-naphthol-pyrazole conjugates have been synthesized through the
-alkylation of 1-(3,5-dimethyl-1
-pyrazol-1-yl)methylnaphthalen-2-ol with methyl iodide, benzyl chloride, methyl ...bromoacetate and
-benzyl-2-bromoacetamide. The aminomethylation of these 2-naphthol-pyrazole conjugates has been examined employing the classical conditions for the Mannich reaction, and also by using
-dimethylmethyleneiminium chloride as preformed aminomethylating reagent. In both situations, aminomethylation of these substrates occurred at
-4 of the pyrazole ring. The bifunctional substrate 1-(3,5-dimethyl-1
-pyrazol-1-yl)methylnaphthalen-2-ol has been chemoselectively aminomethylated in the pyrazole ring using the same preformed aminomethylating reagent.
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