Journal of Chemical Research

Two types of fused pyrimidones, 3-substituted-7-chloro-4H -pyrimido[1,2-b]pyridazin-4-ones and 6-substituted-5H-thiazolo-[3,2-a]pyrimidin-5-ones were easily prepared from Baylis-Hillman adduct acetates under microwave irritation in high yields.

Two routes for the synthesis of the flavone apigenin are described. In the first, taxicatigenin was converted to 2-hydroxy-4,6-dimethoxyacetophenone and then by condensation with anisaldehyde to 2′-hydroxy-4,4′,6′-trimethoxychalcone. The latter was cyclised with iodine and demethylated with pyridine hydrochloride to form apigenin in 53% overall yield. In the second route, a single step for the preparation of the chalcone was used in which 1,3,5-trimethoxybenzene was acylated with p-methoxycinnamic acid. Although the synthesis of apigenin was achieved in a lower overall yield of 34%, the process was simpler.

Citriodora A, 3β,25-dihydroxy-5α,6α-epoxy-7-oxocucurbita-(23E)-en-19-al, a new triterpenoid, has been isolated from the roots of Eucalyptus citriodora, together with five known analogues, which were reported for the first time from this plant. The structures were elucidated on the basis of spectral studies including mass spectroscopy and extensive 2D NMR. All components were tested for anticancer cytotoxic activity against osseous tumour cell line.

Nucleophilic substitution reactions of N -heterocycles such as imidazole, benzimidazole, indole and pyrazole as well as NH₂ or OH containing heterocycles, with electron-deficient aryl halides in the presence of t-BuOK or K₂CO₃ as base and DMSO as solvent are reported. A series of N -aryl azoles, unsymmetric diaryl ethers and diaryl amines were obtained in good yields.

Bis(N-allylbenzimidazol-2-ylmethyl)aniline (L) and its complexes, [Zn(L)(Cl)₂] and [Co(L)(Cl)₂], have been synthesised and the structures of both complexes have been determined. [Zn(L)(Cl)₂] can be described as distorted tetrahedron, while [Co(L)(Cl)₂] has a distorted trigonal bipyramidal geometry. In addition, the complexes were found to possess potent hydroxyl antioxidant activity and be better than standard antioxidants like vitamin C and mannitol. In particular, [Co(L)(Cl)₂] displayed excellent activity towards the superoxide radical.

The incorporation of the 3-methylbenzofuran moiety into the ferrocene nucleus leading to a series of structurally novel hybrids 2-ferrocenoyl-3-methylbenzofuran derivatives has been achieved in good yields of 76-85% through the one-pot Rap-Stoermer reaction of 1-chloroacetylferrocene with 2′-hydroxyacetophenones in refluxing CH₃CN with the presence of K₂CO₃ as base and PEG-400 as catalyst. These newly-synthesised compounds could be good candidates for the development of compounds for use in medicinal chemistry.

Highly conformationally-constrained novel α-amino acid derivatives ((2R/3S) and (2S/3R)-2-(tert-butoxycarbonylamino)-3-cyclohexyl-3-phenylpropanoic acids) have been synthesised with high stereoselectivity (> 90% de) and in 36–37% overall yields. In the synthesis, Evans’ auxiliary (4(R/S)-4-phenyl-oxzaolidin-2-one) was used to control the stereoselectivity via the key reactions of asymmetric Michael addition, azidation and catalytic hydrogenolysis.

The synthesis, photophysical and spectroscopic properties of soluble 2-(ethyl)-1,3-dioxanethio-substituted metal-free and metalloporphyrazines containing Mg(II), Zn(II), Co(II) and Ni(II) are reported. The aggregation behaviour of these compounds was investigated in different solvents and concentrations. The effects of the substituent and the nature of the metal ion on the photophysical parameters of the Mg(II), Zn(II), Co(II) and Ni(II) porphyrazines are also reported.

2,4-Difluoronitrobenzene is reacted with either one or two amines selected from aniline, ammonia, butylamine and benzylamine. All products are characterised spectroscopically and by single-crystal structure determinations. When formed as a minor component alongside 4-dimethylamino-2-(phenylamino)nitrobenzene, 2,4-bis(phenylamino)nitrobenzene crystallises as a hydrogen-bonded hexamer, or paddle-wheel motif, encompassing one-dimensional channels, but as a dense framework when pure. 2,4-Bis(butylamino)nitrobenzene crystallises with the same hexamer motif but with offset sheets.

A facile synthesis of 4,5,5-trimethyl-5,6-dihydrobenzo[c][2,7]naphthyridine, the debrominated analogue of the marine alkaloid veranamine, has been achieved in three steps with a 38% overall yield. from the commercially available 2-bromoaniline. The key benzo[c][2,7]naphthyridine moiety was constructed using a Sonogashira coupling, a tandem Rupe rearrangement–Donnelly–Farrell cyclisation and a Diels–Alder reaction as the key steps. The synthetic strategy allows rapid access to various analogues of veranamine.

A mild Leuckart-Wallach reaction in the presence of catalytic amount Pd/C was developed. Under the optimised reaction conditions, 30% Pd/C loading, 40 °C, 6 atm N₂ atmosphere, racemic 3-hydroxyadamantylglycine ester was obtained in 85% yield. The racemic amino esters were resolved chemically. The ethyl ester was resolved with L-dibenzoyltartaric acid in i-PrOH, give (S)-3-hydroxyadamantylglycine ester in 99% ee and 34% yield. The enantiomerically enriched unwanted isomer was converted to the racemic amino ester and resolved again.

The reaction between aromatic aldehydes, malononitrile and 3-methyl-1-phenyl-2-pyrazoline-5-one catalysed by silica supported perchloric acid nanoparticles (HClO₄-SiO₂ nanoparticles) in solvent H₂O under reflux provided a simple and efficient one-pot route for the synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles in excellent yields.

An efficient synthesis of spiro[indoline-3,7′-pyrrolo[1,2-c]imidazole] is achieved through a three-component reaction of isatins, malononitrile, and hydantoin/2-thiohydantoin in water catalysed by NaHCO₃. All the target compounds were screened for the Cell Division Cycle 25 Phosphatase B (CDC25B) inhibitory activities.

An effective, novel and rapid one-pot three-component route to quinazolin-4(3H)-ones from commercially available starting materials is described. Isatoic anhydride reacts with acyl chlorides and different amines using a combination of trifluoromethanesulfonic anhydride (Tf₂O) and 2-chloropyridine (2-ClPy) to produce the corresponding quinazolinone derivatives in good to excellent yields.

Ruthenium chloride plays the role of a Lewis acid catalyst for the one-pot three-component synthesis of highly functionalised tetrahydropiperidines from aromatic aldehydes, anilines and ethyl acetoacetate in ethanol at ambient temperature without any ligand or activator. The simple experimental procedure, high yields of products, no need for column chromatography, and short reaction times compared to other catalysts are some of the advantages of this method.