Journal of Chemical Research

The syntheses of several kind of natural product skeletal including as ring C aromatic diterpenes, labdane, diterpenoid, purines and tricarbocyclic diterpenes from the diterpenoid (+)-manool are described in this review.

A three-component and one-pot reaction between phenacyl bromide and primary amines in the presence of carbon disulfide to afford substituted 4-hydroxy-4-phenylthiazolidine-2-thiones in high yields.

The complexes [Ln(L)₃(H₂O)₂]_n (Ln=Nd, Sm or Eu; HL= 2-ethoxynicotinic acid) have been synthesised. Structural determinations reveal the complexes to have similar one-dimensional linear chain motifs, which can be further linked into two-dimensional layers via hydrogen bonding interactions. Their three-dimensional luminescence has also been studied.

Some amides and benzylureas can be oxidised to imides and benzoylureas, respectively, using silver(I) nitrate (20 mol %), copper(II) sulfate pentahydrate (20 mol %), ammonium persulfate (3.0 equiv.), and potassium fluoride (20 equiv.) in water at room temperature.

Cyano-N-(2-oxo-1,2-dihydroindol-3-ylidene)acetohydrazide was prepared by condensation of isatin with cyanoaceto-hydrazide in refluxing 1,4-dioxane. Subsequent reaction with a variety of electrophilic and nucleophilic reagents afforded novel heterocyclic compounds and spirooxoindoles. The IR, ¹H NMR and mass spectra of all the synthesised compounds are discussed.

The reaction of 2-[1-(naphthalen-2-yl)ethylidene]hydrazinecarbothioamide with hydrazonoyl halides afforded new thiazole derivatives, whilst reaction with compounds containing an activated double bond such as ethoxymethylene-malononitrile and benzylidenemalononitrile yielded the respective pyrimidine derivatives. A 4-thiazolidin-4-one was obtained by reaction of the hydrazinecarbothioamide with ethyl bromoacetate. Subsequent condensation of the thia-zolidinone with aromatic aldehydes afforded the corresponding arylidene derivatives. Treatment of the hydrazinecarbothioamide with dimethyl acetylenedicarboxylate resulted in the formation of a (methoxycarbonylmethylidene) thiazolinone. Reaction of the hydrazinecarbothioamide with 2-chloro-1,3-dicarbonyl compounds gave the respective thiazole derivatives. The structures of the newly synthesised compounds were confirmed by their elemental analysis and spectral data.

A new series of 3-substituted-9-(1,1′-biphenyl-4-yl)-7-phenyl-7H-pyrazolo[4,3-e][1,2,4]triazolo [4,3-c]pyrimidines and 2-substituted-9-(1,1′-biphenyl-4-yl)-7-phenyl-7H-pyrazolo[4,3-e][1,2,4] triazolo[1,5-c]pyrimidines were synthesised, as a new class of potent xanthine oxidase inhibitors, by oxidative cyclisation of 4-[2-(arylidene)hydrazinyl]-3-(1,1-biphenyl-4-yl)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidines with FeCl₃ in ethanol and Dimroth rearrangement.

A series of 4-aryl-3,4-dihydro-2H-pyrano[3,2-c]quinolin-2,5(6H)-dione derivatives was synthesised by the three-component reaction of aromatic aldehyde, quinoline-2,4-diol and Meldrum's acid catalysed by l-proline. This protocol has the advantages of easy work-up, mild reaction conditions and high yields.

Porous chitosan microspheres-supported palladium catalysed the amination of aryl halides with a wide variety of secondary amines to yield the corresponding cross-coupling products under aerobic conditions. Both aryl bromides and iodides gave good to excellent yields of N,N-disubstituted anilines. The procedure can tolerate common functional groups such as chloro, methoxyl and nitro. The heterogeneous catalysis is efficienct and the catalyst could be recycled seven times without obvious decreased conversion.

An efficient reaction of epoxides with carbon dioxide to generate the corresponding cyclic carbonates employing pentaerythritol/KI, does not need solvent.

An efficient and highly enantioselective synthesis of 3-hydroxy-4-phenylbutan-2-one was developed involving the asymmetric epoxidation of an enone and hydrogenolysis of an α,β-epoxyketone. 1-Phenyl-3-buten-2-one was epoxidised with t-butyl hydroperoxide using a chiral La-BINOL-Ph₃P=O complex as the catalyst to give (3S,4R)- or (3R,4S)-3,4-epoxy-4-phenylbutan-2-one in ~90% yield and 97% ee. The resultant optically active epoxyketone was reduced in the presence of Pd/C (5 mol%) and H₂ (3 bar) in THF at room temperature to produce (S)- or (R)-3-hydroxy-4-phenylbutan-2-one in ~80% yield with more than 90% enantiomeric excess.

A novel synthesis route for telithromycin was developed based on a 11,12-cylic carbonate protection strategy to prevent formation of 9,12-hemiacetal by-product. Through a 11,12-carbonate-6-O-methylerythromycin intermediate, telithromycin was synthesised from 6-O-methylerythromycin in five steps with 33% overall yield.

Novel substituted chromenes, chromenopyrimidines and chromenotriazolopyrimidines were synthesised to explore their anticancer activity. Several compounds were evaluated for their antitumour activity, most of them revealed promising cytotoxic activity against breast cancer cell line MCF-7 in comparison to colchicine as positive control.

4-Alkyl-3,4-dihydropyrimidin-2(1H)-ones possess a number of important properties in comparison with their 4-aryl analogues. We show that these compounds can be synthesised by a simple one-pot reaction of urea or thiourea, different aliphatic aldehydes (from acetaldehyde to valeraldehyde) and various dicarbonyl compounds (ethyl acetoac-etate, pentane-2,4-dione, N-(4-chlorophenyl)-3-oxobutanamide, acetoacetaldehyde dimethylacetal) in refluxing DMF or HOAc without use of any catalyst. The methylation of 4-alkyl-5-C(O)R-3,4-dihydropyrimidin-2(1H)-ones leads to 1-methyl derivatives.

A one-pot condensation of an aldehyde with 1,2-phenylenediamine or 2-aminothiophenol in dimethyl carbonate at 100 °C under O₂ in the presence of catalytic amounts of CeCl₃–NaI gave an imine intermediate, which cyclised and dehydrogenated to give 2-arylbenzimidazoles or 2-arylbenzothiazoles in good yields.

A rapid and efficient regioselective α-chlorination of a new series of β-dicarbonyl compounds using a commercial solution of sodium hypochlorite in the presence of K₂CO₃ in THF at 0 °C, is reported. With prolonged reaction times, α-chloro β-keto esters, bearing an acyl moiety, undergo a tandem chlorination–deacylation reaction, affording the corresponding α-chlorinated esters.