European Journal of Organic Chemistry

This microreview summarizes our progresses over the last years in the chemistry of 1,2-diaza-1,3-dienes and outlines some of the reactive peculiarities that make this class of compounds powerful tools inheterocyclic chemistry.

An effective way to produce six- and seven-membered heterocycles from epoxy alkynes catalyzed by gold(I) or Yb(OTf)₃/gold(I)through selective carbon or oxygen nucleophilic addition to alkynes has been described.

The total synthesis of (±)-cyclocolorenone (2) (an aromadendrane) was achieved in seven regio- and stereocontrolled steps via hydroazulenone 6 (a versatile intermediate), through efficient C-1 epimerization,selective C-8,9 hydrogenation, and stereocontrolled construction of the aromadendrane core. Reduction of 2 led to (±)-α-gurjunene.

Herein is reported the first anodic oxidation method for the cleavage of primary and secondary alkyl para-methoxyphenyl ethers. Under a controlled potential (1.7 V) and in the presence of NaHCO₃, this reaction tolerates oxidation and acid-sensitive functions, thus constituting an efficientmethod for the orthogonal deprotection of para-methoxyphenyl ethers.

Carbamoselenoates having a buta-2,3-dienyl or penta-3,4-dienyl group on the nitrogen atom was found to undergo intramolecular selenocarbamoylation of an allene unit in the presence of a palladium catalyst to give rise to the corresponding α,β-unsaturated lactam having an allyl selenide unit.

Asymmetric arylation of ethyl 4,4,4-trifluoroacetoacetate catalyzed by a chiral Brønsted acid was developed to give tertiary alcohols in good yields with moderate enantiomeric excesses, which can be improved to 99.9 % by single recrystallization.By extending this protocol to ethyl trifluoropyruvate, the direct arylation reactions proceeded well to afford the desired products in quantitative yields with 20–62 % ee.

A perfect match of reagents (sulfoxides, nitriles and trifluoromethanesulfonic anhydride) allows a Ritter-like process for the preparation of fluorinated sulfilimines or sulfoximines. This versatile, solvent and metal free, reaction is an opening way through the synthesis of new ligands or electrophilic trifluoromethylating reagents.

6-Aminopenicillanic acid (6-APA) and two of its derivatives have been evaluated ascatalysts for use in direct cross-aldol reactions for the first time.

Structurally different isoquinolin-3-ones could be selectively synthesised through a three-component, Pd-catalysed reaction starting from aryl iodides, chloroamidesand properly substituted olefins. An important beneficial effect of water on reaction selectivity was observed.

A series of fluorinated gemini pyridinium amphiphiles have been prepared and fully characterized. The use of different characterization techniques, such as conductivity and surface tension measurements, shed light on the aggregation process. The title products showed interesting, unusual properties that are important for possible applications in gene therapy.

A theoretical study of the HIV-1 inhibitor BMS-378806 was performed at the B3LYP/6-31G(d) level and the results were supported through high-field ¹H NMR at 248 K. Four conformational families were located by the calculations and four distinct series of signals were detected in the ¹H NMR spectrum.

The indazole ring is practically unreactive toward Friedel–Crafts reactions. However, under suitable conditions, it reacts with aliphatic aldehydes and p-toluenesulfinic acid to give the corresponding sulfonyl indazoles. This unprecedented process provides easy access to 3-substituted indazoles that can be further desulfonylated under reductive conditions to give 3-alkylindazole derivatives.

By choosing the right additives, the title compounds were found to efficiently catalyse the hydroarylation of alkynes at roomtemperature and with controllable selectivity

Inexpensive, commercially available Lewis acids (LA) can efficiently activate metal halide precursors for asymmetric catalysis as demonstrated for the asymmetric Ni-catalysed hydrovinylation of styrene. In caseof InI₃ as LA, the performance of the easily generated catalytic system is equal or even better than that of the state-of-the-art Ni/BArF catalyst.

From the second-order rate constants of the reactions of the aryl-substituted para quinone methides (Ar-QM) with stabilizedcarbanions, electrophilicity parameters E as defined by log k = s(N + E) have been determined.

New ethynyl- and butadyinyl-bridged bis(phthalocyaninates), peripherally functionalized with strong donor moieties, have been synthesized. The attachment of six butoxy groups to each phthalocyanine core increases the solubility and electron richness for optical properties, further the formation of regiosomers is precluded. Preliminary Z-scan experiments have been also performed on binuclear Pb^II complexes to evaluate their optical limiting capabilities.

A modular approach to the synthesis of unsaturated carbonyl motifs is reported with the design and use of a bifunctional olefinic template. A small olefin unit, (E)-1,2-disilylethene 5, was activated selectively andsequentially by transition-metal catalysis to give a series of diverse and conjugated α,β-unsaturated ketones through a coupling/acylation sequence.

The application of the halogen dance reaction for the synthesis of starting materials for cross-coupling reactions is reported. The obtained compounds were then successfully applied in sequential Stille and Suzuki–Miyaura cross-coupling reactions to obtain novel thiazole derivatives.

A number of new specific merocyanine-type dyes have been obtained by incorporating polymethine substituents into the meso position of BODIPY. The prepared dyes show intense long-wavelength absorption and weak fluorescence.

By using (R)-1-phenylethylamine as a chiral molecule and 1-pyrenesulfonic acid as a fluorescent molecule, a chiral supramolecular organic fluorophore composed of a 2Dlayered structure was successfully developed. This chiral supramolecular fluorophore possesses circularly polarized luminescence properties (CPL) in the solid state.

A novel organotin reagent supported on an ionic liquid is applied to a number of Stille cross-coupling reactions to afford biaryl compounds. The products, which are obtained in high yields at low temperature under solvent- and ligand-free conditions, may be easily purified. The catalyst retains its activity for up to five reactions. A catalytic cycle is proposed, which also explains the formation of side products.

4-Subsituted dihydropyrimidinones were synthesized through highly regio- and chemoselective addition reactions of carbon nucleophiles in a synthetically useful manner.

Direct alkylation of adenosine with methyl p-toluenesulfonate furnishes a mixture2′/3′-O-methyladenosine regioisomers which upon enzymatic acylation with Pseudomonas cepacia lipase selectivelyyields acylated 2′-O-methyladenosine. Chromatographic separation and hydrolysis of the latter offers easy access to 2′-O-methyladenosine.

To support the cooperative bimetallic mechanism of the ring-opening of meso-epoxides with TMSN₃, symmetrical salen–Cr^III complexes were immobilized on hyperbranched polyglycerol. Further investigations were performed to understand the influence of the length of the linker between polymer and catalyst. Higher eevalues were obtained with longer linkers.

Two new bicyclic fusidilactones D and E have been isolated, along with the known fusidilactone B, from the fungal endophyte Fusidium sp. The relative configuration of the latter was established by X-ray diffraction and the absolute configurations by TDDFT calculations of CD spectra using the solid-state CD/TDDFT approach. The metabolites showed antifungal, antibacterial, and antialgal activities.