European Journal of Organic Chemistry

In this review we describe transition-metal-catalysed and -mediated processes for the preparation of oxindoles from anilides through C(3)–C(3a) bond formation. Traditional methods and recent developments are presented, including their applications in natural product synthesis.

A highly unusual transmissive olefination of α′-hydroxynitriles is triggered by Grignard reagents through the formal ejection of hydroxide. The rapid synthesis of stereodefined alkenenitriles is illustrated in a four-step synthesis of the proposed structure of morinol I.

A metal-free domino reaction for the synthesis of a new family of fused bicyclic 1,4-diazepanes and 1,5-diazocanes has been developed. This reaction involves the use of N,N′-dialkylated diamines as the nitrogensource, through-space orbital interactions between the two nitrogen atoms as the reactivity director element, and a diversely functionalized activated skipped diyne as the reactive platform.

The catalytic enantioselective addition of MeMgBr to aldehydes with readily available ligand (S_a,R)-L1 leads to the very versatile methyl carbinol unit in unprecedented yields and enantioselectivities. Moreover, the methodology proves to be effective for a variety of alkyl Grignard reagents. Chiral alcohols are obtained in a simple one-pot procedure and under mild conditions.

The classical Arbuzov reaction has been improved by using microwave activation and by the addition of salt. The changes have allowed the synthesis of six-membered cyclic-phosphonates (phostones) as internucleotidic linkages with defined, restrained non-canonical alpha and beta torsion angles.

We report the convergent preparation of four hexasaccharides to be used towards the synthesis of a safe anticancer vaccine based on the tumor-associated carbohydrate antigen dimLe^x. A common trisaccharide intermediate was first synthesized as a precursor to the tetrasaccharide backbones. These tetrasaccharides were then converted into diol acceptors and fucosylated at O-3 of both glucosamine residues.

A protecting-group-free two-step approach for the preparation of tetrahydroquinolines has been developed and applied in total syntheses of the alkaloids (+)-angustureine and (–)-cuspareine. The procedure involves a highly regio- and enantioselective intermolecular iridium-catalyzed allylic amination followed by one-pot hydroboration and intramolecular Suzuki–Miyaura cross-coupling.

Five different reactions between two partners – the carbanions of α-alkoxy-α-phenylacetonitrile and o-chloronitrobenzene – are fully controlled by the reaction conditions. This is an example of the unique versatility of the reaction of nucleophiles with nitroarenes.

Ligands 20–23 were prepared and used for the asymmetric transfer hydrogenation of a range of ketones. Using ligand 23, bicyclic ketones were reduced in up to 96 % ee.

A direct synthesis of indole-2-carboxylate derivatives involving the Pd^II-mediated annulation of 2-iodoanilines onto an alkoxyacrylate derivative is described.

Pyridopyrimidine, pyranoquinoline, and phenanthroline derivatives can be easily and efficiently synthesized under mild, efficient, and simple reaction conditions by the direct reaction of a 1-aminopenta-1,4-diene fragment, an aromatic aldehyde, and BF₃·OEt₂ in the absence of any metal catalyst in good to high yields. The process involves a BF₃·OEt₂-catalyzed 1,3-hydride shift followed by 6π electrocyclization.

Carboxylic acids can be selectively converted into amides in the presence of thiols and alcohols through carboxyl activation by phosphoryl iodide, which is formed in situ from P(OMe)₃ and I₂. The chemoselectivity and generality of the method, the low cost, wide availability of reagents, and the ease of use make it a very favorable process.

The synthesis of chiral N-oxide organocatalysts and their evaluation in the asymmetric allylation reaction of aromatic and α-β-unsaturated aldehydes with allyltrichlorosilane is reported. These readily modifiable organocatalysts are based on the tetrahydroisoquinoline framework. The chiral homoallyl products were obtained in good yield and high enantioselectivity under mild reaction conditions.

A new temperature-dependent domino-Staudinger/aza-Wittig/isomerization reaction was developed to construct 1,2,4-triazino[2,3-b]indazoles or 3H-1,4-benzodiazepines.

Readily available exo-glycal derivatives can be transformed into more highly elaborated ones through vinylic bromination and palladium-catalysed cross-coupling. Chemical manipulation and stereoselective hydrogenation of new selected derivatives afforded access to C-glycosides in a stereoselective manner.

Fused 1,4-dihydropyridines and 1,2-dihydropyridines were selectively and conveniently synthesized through domino four-component reactions of arylamines, acetylenedicarboxylate, aromatic aldehydes, and cyclic 1,3-diketones.

Synthetically useful 1-acyl-1H-pyrroles are used as ester surrogates with heightened reactivity to enable the construction of fused and non-fused pyranones from aliphaticaldehydes using the Stetter reaction. Additionally, the 1-acyl-1H-pyrroles are compatible with aromatic aldehydes and facilitate the intermolecular Stetter reaction involving both aromatic and aliphatic aldehydes.

The complexation of various ditopic octaamine ligands for glyphosate recognition has been studied by potentiometric titration as well as calorimetry and NMR measurements. The results unambiguously show the selectivity of a cyclic–open-chain polyazaligand (cyclam–1,4,8,11-tetraazaundecane) for the well-known herbicide glyphosate compared with its symmetric analogues.

Silylated 2,7-dioxabicyclo[2.2.1]heptanes have been efficiently synthesized in highyields by a tandem reaction involving epoxidation of oxoallylsilanes and subsequent cyclization to give the epoxy-bridged tetrahydropyran derivatives. The same reaction with the corresponding oxovinylsilanescleanly gave silylated epoxy ketones, which do not undergo cyclization.

A diversity-oriented synthesis is described for highly functionalized chiral building blocks and biologically active iminosugars starting from common intermediate 1a and obtained through a regioselective reductive cleavage of a bis(benzylidene) acetal.

Acridine derivatives can be used to modify the biological activity of sulfur-containing peptides. A large set of acridine derivatives have been investigated by density functional calculations, which revealed that correlations between reactivity, geometry, and substitution pattern can enhance the design of new acridine labels as well as the computer search for the transition state.

An efficient tandem process for the selective synthesis of 1,2-annulated α-fused quinoxalines using benzotriazole methodology by modified Pictet–Spengler reaction is described. This approach also provides a novel tandem synthesis of ring-fused quinoxalinones.

The synthesis and properties of four trichromophore systems containing boron dipyrromethene as a central unit connected to a porphyrin unit through the 3-position and a core-modified porphyrin or an expanded porphyrin through the 5-position, are described.