Letters in Organic Chemistry - Volume 5, Issue 1, 2008

Norfloxacin ethyl ester was prepared from 3-chloro-4-fluoroaniline in ionic liquid in a one-pot procedure by condensation with EMME [ethoxymethylenemalonic diethyl ester], cyclization, ethylation and condensation with anhydrous piperazine. After its hydrolysis, norfloxacin was obtained with an overall yield of 72.7%.

The synthesis of a novel series of isatin derivatives bearing an acetamide group is described. These 2-(2,3- dioxo-indolin-1-yl)acetamide derivatives were synthesized by N-carboxymethylation of isatin followed by conversion of the carboxylic acid function into a tertiary amide. In a preliminary study, this series of compounds were tested in vitro for their biological activity, against various strains of bacteria.

A straightforward access to 2-halogenoimidazoles via a N-THP protection was described in this paper. The NTHP protecting group is easily introduced by reaction of 2-chloro-THP with imidazole. Lithiation followed by reaction with an appropriate electrophile affords 2-halogeno N-THP derivatives. The THP protecting group is then cleaved to get the title compounds in good to high yields.

C2-dissymmetric PyOX-ligands have been applied to the asymmetric Henry reaction. This widely applicable reaction is easy to perform, requires no inert atmospheres or dry solvents, and gives good selectivities. By adjusting ligand side-chains, a significant impact on selectivities was observed.

Electrophile-induced cyclization of steroidal δ-alkenyl oximes and oxime ethers and subsequent hydride reduction of the cyclic nitrones led to new halogenated or selenylated N-hydroxy- or N-benzyloxy-aza-D-homo-estrones. Starting from a 13β-D-secoestrone oxime or oxime ether, steroidal dimers were isolated in intermolecular 1,3-dipolar cycloaddition of the cyclic nitrone to the C=N double bond of the oxazepine intermediates.

Reaction of 2,4-diaryl-2,3-dihydro-1H-1,5-benzodiazepines 1 either with acetyl chloride in dry CH2Cl2 in the presence of pyridine, or with acetic anhydride in the presence or absence of base afforded, after unexpected opening of the benzodiazepine ring, N-butenylidene-amino-phenylacetamides 3 in excellent yields instead of the expected ring tautomers 2.

A new selective reduction of N-substituted phthalimides to the corresponding hydroxyl lactams is described. This reduction performed smoothly under mild, concise and easily controllable condition in good yield (up to 97%). The generality of the reduction was also investigated and a wide range of substrates were suitable for this reaction.

This paper describes the O-glycoside formation from 1-hydroxy sugars by the bismuth(III) triflate-catalyzed dehydrative glycosidation. The reactions of the 1-hydroxy sugars with some primary alcohols in the presence of only 5 mol% bismuth(III) triflate at reflux for 15 min in dichloromethane afforded the O-glycosides in good yields. This paper clarifies several important properties during the bismuth(III) triflate-catalyzed dehydrative glycosidation using 1-hydroxy sugars.

Carbamates were reacted in one pot with aromatic aldehyde and ketones at ambient temperature in the presence of catalytic amount of Zr(OTf)4 to furnish the corresponding N-protected β-amino-β-aryl ketones in good yields.

A series of highly functionalized naphthoquinones was prepared by an original tetrakis-SRN1 reaction involving 2,3,6,7-tetrakis(chloromethyl)-5,8-dimethoxynaphthalene-1,4-dione with various nitronate anions and S-centered anions.

Several compounds containing in the same molecule a hydrazyl moiety and a nitrone (or a nitroxide moiety) were characterised by different means, as visible spectroscopy, hydrophobicity, cyclic voltammetry, bond dissociation energy (BDE), electron paramagnetic resonance spectroscopy (EPR), and pKa values, in order to evaluate them as sensors and probes for monitoring acid-base, redox, and free radical processes.

A convenient and green protocol for the synthesis of quinolines by Friedlander annulation using an acidic ionic liquid, ethylammonium nitrate, as both a catalyst and a reaction medium is reported. The reactions were performed at 45°C with moderate to excellent yields. The recovered ionic liquid could be reused for several cycles without any loss of activity.

A variety of bicyclo-heterocyclic compounds have been synthesized by ondensation of phthalic acid, homophathalic acid, 1,2-phenylenediacetic acid, 2,3-pyridine dicarboxlic acid, 3,4-pyridine dicarboxlic acid and 2,3-pyrazine dicarboxlic acid with 1-(2-aminoethyl)-piperidine and furfuryl amine, in one step using microwave irradiation technique. Bicyclo-heterocyclic compounds were obtained within minutes in good chemical yields and high purity.

Phosphine-catalysed [3+2] cycloaddition of ethyl buta-2,3-dienoate and 4-quinolone-1,3-dicarboxylate furnished the (3aS,9aR)-triethyl 9-oxo-9,9a-dihydro-1H-cyclopenta[b]quinoline-3,4,9a(3aH)-tricarboxylate.

Treatment of piperidine 8 with acetyl chloride or ethyl chloroformate in the presence of triethylamine gave the 2,3-dehydrogenated products 10a and 10b, respectively, together with the expected N-acylpiperidines 9.

A facile and efficient one-pot synthesis of polyhydroquinoline derivatives via the Hantzsch reaction using a variety of aldehydes, 5,5-dimethyl-1,3-cyclohexanedione or 1,3-cyclohexanedione, ethyl acetoacetate, and ammonium acetate in the presence of potassium dodecatungstocobaltate trihydrate [K5CoW12O40. 3H2O] as a heterogeneous catalyst in a solvent-free media at 90 °C is described herein . The present methodology offers several advantages such as excellent yields, simple procedure, shorter reaction times (10-25 min.), milder conditions and the catalyst exhibited remarkable reusability.

The solvent-free reaction of [60]fullerene with phenylhydrazine hydrochlorides 1a-e in the presence of sodium carbonate under high-speed vibration milling conditions afforded 1-aryl-1,2-dihydro[60]fullerenes 2a-e, amongst them 1- (4-nitrophenyl)-1,2-dihydro[60]fullerene 2e could not be obtained in the liquid-phase reaction. When excess sodium nitrite was employed to replace sodium carbonate, fullerotriazoline 3 was formed. Product 3 tended to decompose via the loss of molecular nitrogen to give azafulleriod 4.

In this work we synthesized the aggregation pheromones (S)-2-methyl-4-octanol and (4S, 2E)-6-methyl-2- hepten-4-ol in high enantiomeric excess applying as the key step an enzymatic resolution of 5-methyl-1-hexyn-3-ol.