European Journal of Organic Chemistry

The cover picture shows that oligonucleotide conjugates with different biomolecules or markers could be obtained through the reaction between a thiol function of the oligonucleotide and an acrylamide function of the biomolecule or marker according to a Thiol-Michael-Type Addition (TMTA). This reaction could be combined sequentially with a Copper(I)-catalyzed Azide–Alkyne Cycloaddition (CuAAC) affording bis-conjugated oligonucleotides. These “click” reactions allow the preparation of a bouquet of molecules where their stem is a DNA sequence. This picture was inspirited by Picasso's “Bouquet with Hands”. The background is an autumn view of the countryside of Montpellier. Details are discussed in the article by F. Morvan et al. on p. 465 ff. The cover picture was elaborated by Thibault Morvan.

Over the last decade, four precursor types have been established as broadly general substrates in heterocycle synthesis. By appropriate choice of catalyst and coupling partner, these four precursor types can be converted into a wide range of aromatic products.

Pd⁰/PR₃ complexes promote C–C bond formation with organoboronates through C–F bond activation of fluorinated alkenes. Mechanistic studies show that a Pd^II fluoride intermediate plays an essential role in this base-free cross-coupling reaction. Moreover, a Ni(NHC) catalyst is efficient for C–C coupling through C–F bond cleavage of fluoroarenes.

An efficient ligand-assisted palladium-catalyzed approach for the straightforward synthesis of the pyridin-2(1H)-one framework was developed. This method provides one of the easiest pathways to access this class of valuable compounds from easily available starting materials (2-chloropyridines). A possible mechanism for this reaction is discussed.

A one-pot multicomponent reaction involving the reaction of an isocyanide with an in situ generated dihydropyridinium salt permits a straightforward access to a biomimetic model of the recently isolated halichonadins K and L.

Organocatalytic asymmetric Michael addition of oxazolones 2 to vinylogous imine intermediates generated in situ from arylsulfonyl indoles 1 is described. This protocol provides facile access to optically active 3-indolyl derivatives with good results. The resulting adducts can be easily converted into syn-α,β-disubstituted tryptophan derivatives without compromising the stereoselectivities.

Highly substituted 9- and 10-selenylphenanthrenes are easily prepared from the corresponding selenium-containing (o-phenylaryl)alkynes. The selectivity is perfectly controlled by indium(III) and gold(I) catalysts. Various substrates can be converted into phenanthrene derivatives with high selectivity and in good yield under very mild conditions.

Oligonucleotide conjugates bearing different labels were synthesized by mono- or poly-Thiol Michael-Type Additions (TMTAs) through the use of acrylamide derivatives. Bis-oligonucleotide conjugates were obtained with a combination of TMTA and CuAAC “click” chemistry.

4-Alkenyl-2-aminothiazoles act as in-out dienes in [4 + 2] cycloadditions with a wide variety of dienophiles. The reactions were endo-selective when cyclic dienophiles were used and regioselective with unsymmetrical dienophiles. A stepwise mechanism is proposed for the cycloadditions with acyclic dienophiles.

Preparations of benzannulated cycloheptanones starting from binaphthyl molecular platforms are described.

A set of star-shaped chromophores containing functionalized fluorene units were synthesized and shown to possess ascending two-photon absorptivities with the growth of their π systems. The observed effective optical power-limiting and stabilization behaviors in the nanosecond time domain indicate that these dye molecules have potential as broadband and quick-responding optical limiters.

Synthesis of highly thermally stable energetic nitrogen-rich polymers incorporating tetrazole heterocycles and the corresponding polymer precursor is reported. Complete structural and spectroscopic characterization including IR and multinuclear NMR spectroscopy and mass spectrometry, as well as single-crystal X-ray diffraction analysis of 1,2-bis(5-carboxyethyl-1H-tetrazolyl)ethane, was accomplished.

An efficient method using a bimetallic MnF₂/CuI catalyst in combination with trans-1,2-diaminocyclohexane as the ligand has been developed for the cross-coupling of benzamides and sulfonamides with differently substituted aryl iodides in water. The corresponding N-arylated products were obtained in good to excellent yields (up to 97 %) under the catalytic conditions.

The stereoselective total synthesis of dinemasone A was accomplished in a longest linear sequence of 14 steps using double-intramolecular hetero-Michael addition as the key spiroketalisation reaction.

A synthetic method was developed for the preparation of vinyl sulfides and vinylamines. Arylalkynyl phenyl sulfides and sulfonamides underwent a catalytic intramolecular hydroarylation reaction to give 1,2-dihydronaphthalenes, 2H-chromenes, and 1,2-dihydroquinolines with a phenylsulfenyl or N-phenyl-N-tosyl group on the sp²-hybridized benzylic carbon.

New planar chiral bis(heterocyclic) N-donors based on the rarely investigated class of [2](1,4)-benzene[2](2,5)pyridinophanes were synthesized. The synthesis of the pyridinophane scaffold was simplified, and a pyrazole, triazole, tetrazole, and pyrimidine heterocycle were successfully attached to the planar chiral backbone.

Fluorescent β-arylalanine derivatives were prepared in good yields using a rhodium-catalysed conjugate addition of arylboronic acids to N-protected dehydroalanines. The photophysical properties of some of the β-arylalanines were studied in solvents of different polarities. Considering the high fluorescence quantum yield of these compounds, some of them may be useful as fluorescent markers.

A carica papaya lipase catalysed resolution of N-protected β-phenylalanine esters has been developed. High enantioselectivity was achieved by two strategies that involved engineering of the substrates and optimization of the reaction conditions. After 50 % conversion, the products were separated and used as key chiral intermediates for the synthesis of (S)-dapoxetine with > 99 % ee.

Various allyl ethers of 1,4-anhydro-D-sorbitol and pentaerythritol underwent self-metathesis reactions to give oligohydroxy dimers useful as new components for alkyd resin formation.

The stereoselective total syntheses of (+)-aspergillide B and (+)-7-epi-aspergillide A were achieved. The key reactions include Noyori's asymmetric transfer hydrogenation, an Achmatowicz rearrangement, a Ferrier-type alkynylation, a hydrosilylation–protodesilylation, a CBS (Corey–Bakshi–Shibata) oxazaborolidine reduction, a Yamaguchi macrolactonization, and a Mitsunobu macrolactonization.

Chitosan aerogel, derived from the abundant natural biopolymer chitin, has been used as a heterogeneous amine catalyst for the asymmetric aldol reaction in water. The combination of fatty acids and surfactants as additives in the reaction had a strikingly beneficial effect on the reaction outcome, especially when heterocyclic ketones were used as donors.

An efficient and high-yielding, one-pot, Cu-catalyzed synthesis of 2-indolyl-C-glycosides is delineated. The sequence involves a cascade Sonogashira type coupling and a hydroamination reaction between sugar-derived alkynes and N-tosyl-o-iodoaniline followed by the removal of the N-tosyl group to provide a library of 2-indolyl-C-glycosides in moderate to excellent yields.

The samarium diiodide promoted reduction of 3,6-dihydro-2H-1,2-oxazine derivatives not only provides the expected acyclic 1,4-amino alcohols but also electron-rich pyrroles. The latter products are formed by a surprising ring contraction that probably involves an intramolecular hydrogen shift.

The twist conformation in biphenyl results from a balance between the stabilization arising from electron delocalization, which favors a planar structure, and steric repulsion, which favors a perpendicular structure. The two competing forces have nearly the same magnitude.