European Journal of Organic Chemistry

Four elemental reactions have to date been applied for the cleavage of C–C single bonds by transition metal complexes: (i) oxidative addition, (ii) β-carbon elimination, (iii) retro-allylation, (iv) migratorycarbonyl extrusion. These reactions, their mechanisms, their limitations and their potential are presented in this review along with (still rare) examples.

Isomerization of the second-ring Diels–Alder adduct to the central-ring adduct in the reaction of pentacene and tetracyanoethylene is reported. Photoisomerization can be induced in both directions, whereas thermal isomerization can be induced only from the second-ring adduct to the central-ring adduct.

The addition to various olefins through a one-pot cascade oxidation–addition reaction to give sulfonylethanone oximes by using N-hydroxysulfonamides as a source of nitrogen and sulfur is reported. This method towards sulfonyl oximes proceeds in good yields with styrenes possessing either electron-donating or -withdrawing groups and constitutes an interesting functionalization of olefins.

The reactions of O-α-glycosyl trichloroacetimidates and thiols with phenylboron difluoride as catalyst afford, without the support of anchimeric assistance, mainly β-thioglycosides. Clearly, the phenylboron difluoride–thiol adducts are responsible for this S_N2-type reaction leading to a reversal of the anomeric configuration compared with standard glycosidation methods with thiols as acceptors.

Enantioenriched P-stereogenic phosphanes or phosphane boranes were obtained in high yield by facile stereospecific reduction of diastereomeric alkoxyphosphonium salts (DAPS) formed by the dynamic resolution of phosphanes under Appel reaction conditions.

The catalytic direct aldol reaction of pyruvic aldehyde dimethyl acetal and 2-acetylthiazole with sugar aldehydes is demonstrated to be the key step in the synthesis of 3-deoxy-2-ulosonic acids.

A straightforward synthesis and kinetic resolution sequence is applied to protected methyl glycosides using lipases and nonenzymatic methods. Oxidation and hydrocyanation were combined in a one-pot procedure and the crude product was subjected to lipase-catalyzed acylation. The net effect is a stereoselective C–H substitution with a nitrile group at position 6 of the protected starting material.

We have synthesized a series of halogen-end-capped oligo-phenylene-ethynylenes to study interactions at the solid/liquid interface and in crystal structures. Here we probe the interplay and diversity of intermolecular interactions between halide end-groups and oligo-phenylene-ethynylene backbones through solution depositions (2D) and X-ray crystal structures (3D). The STM images and crystal structures reveal a striking complementarity in each case.

A series of indenofluorene derivatives incorporating the (diphenylamino)arylvinyl group and di-tert-butylphenyl blocking units have been synthesized and their photophysical and electroluminescent properties examined. In the case of device 3C, the use of 3 as dopant in the emitting layer led to blue emission with an external quantum efficiency of 7.8 % at 20 mA cm^–1.

Increasingly cyanated 1,1-dicyano-4-(N,N-diethylanilino)-substituted buta-1,3-dienes were synthesized by unusual routes and characterized by X-ray analyses. Their opto-electronic properties strongly depend on both the number and position of the additional CN groups. Substitution in positions 2 and 4 affects the intramolecular charge-transfer bands more strongly than substitution in position 3, which is rationalized by theoretical calculations.

The first examples of highly regioselective iodine-mediated nitro-alkyne cycloisomerization to afford fused isoxazoles are presented.

A concise method for the asymmetric vinylation of enals is disclosed that employs β-nitroethyl phenyl sulfone as a new synthetic equivalent for the vinyl anion.

An enantioconvergent strategy was developed by using a C₂-symmetric element within the chiral pool and by applying an iodine-promoted cyclization of an unsaturated carbonimidothioate for the regio- and diastereocontrolled installation of amino and hydroxy units. (+)-Valiolamine (1) and (+)-valienamine (2) were synthesized from commercially available D-tartaric acid by using this strategy.

Calix[4]arenes with two iminophosphorane units tethered at their upper rims have been synthesised for the first time and used in palladium-catalysed cross-couplings between phenylboronic acid and aryl halides. The good performances of the ligands possibly arise from their capacity to form chelate complexes in highly crowded metal environments.

1,4-Dipoles originating from reactions between pyridines and activated alkynes react with N-protected isatylidene derivatives to afford 1′,9a′-dihydrospiro[indoline-3,2-quinolizin]-2-one derivatives in excellent yields and with good diastereoselectivities. This new synthetic strategy is an efficient method for the construction of the spiro[indoline-3,3′-piperidin]-2-one skeleton.

Two different types of 2,1,3-benzothiadiazole (BTD) derivatives were introduced into DNA. Depending on the electronic properties of the BTD units, the DNA hybrids exhibit significantly different spectroscopic profiles. Fluorescence quenching by the individual nucleobases correlates with the respective oxidation potentials.

A very simple, direct, bismuth-catalyzed 1,4-conjugate reduction protocol thatallows for the catalytic regioselective formation of substituted ketones from enones under mild conditions has been developed.

Six new vobasinyl-iboga bisindole alkaloids and eight known compounds have been isolated from the stem bark ofMuntafara sessilifolia. Their structures were elucidated by NMR and MS and three of them were found to bear an unprecedented α-amino aldehyde group. The biosynthetic origin of these bisindoles is proposed. Their antiplasmodial and cytotoxic activities have been evaluated.

The highly strained 1,3-fused polycyclic cyclopropene 25 favors the ring-opened vinylcarbene form, which undergoes a number of reactions including addition of water, insertion into the C–H bond α to the oxygen atom in THF to yield exo products, and [1+2] addition to the C=C bond in furan, preferentially forming the endo adduct. Furthermore, on heating, the addition products 27 and 28 rearrange to aldehyde 29.

The bis(triflate) ester of 4,5-diiodobenzene-1,2-diol provides a useful synthon for the preparation of unsymmetrical tetraalkynylarenes.

1,3-Heterocycles have repeatedly been considered as hydrolytically cleavable precursors for the release of fragrant aldehydes or ketones. Dynamic headspace analysis above a cotton surface showed that glycinamide-based imidazolidinones represent in practical applications a good compromise between precursor stability and release efficiency.