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Densely functionalized polyether macrocycles can be prepared in one pot in yields up to 60% by the rhodium(II)-catalyzed decomposition of methyl diazoacetoacetate in the presence of a variety of substituted or unsaturated 5- and 6-membered ring cyclic ethers. A comprehensive analysis of the solid state conformations of the macrocyclic geometries is detailed as well as novel mechanistic insights about the multi-component condensation reaction.

Enantiopure binaphthyl azocines can be prepared in a single step via the direct copper-catalyzed reaction of binaphthyl azepines and α-diazo carbonyl reagents. The [1,2]-Stevens rearrangement is general (61-93% yields) and can be extended to [3]ferrocenophanes; similar reactivity in favor of the products of ring expansion is obtained with these ferrocene derivatives (80-96% yields).

An unusual palladium hydride complex has been shown to be a competent catalyst in the isomerization of a variety of terminal and internal epoxides. The reaction displayed broad scope and synthetic utility. Experimental and theoretical evidence are provided for an unprecedented hydride mechanism characterized by two distinct enantio-determining steps. These results hold promise for the development of an enantioselective variant of the reaction.

International audience; Transfer news: The use of a simple method allows the various sensitization steps in Eu(III) -containing complexes to be deciphered. Incorporation of an increasing number of electron-withdrawing fluorine atoms on the rigid and electronically tunable phenyl spacer between two tridentate binding units (see picture, red O, dark blue N) affects the quantum yield, intersystem crossing, and energy-transfer processes in a rational way.

A high-yielding enantioselective semipinacol transposition, initiated by an electrophilic iodination event is described.

This novel highly enantioselective title reaction affords a wide range of fluorinated spirocyclic derivatives by using the new BINOL derived phosphoric acid (BIN).

Enantiopure binaphthyl azocines can be prepared in a single step via the direct copper-catalyzed reaction of binaphthyl azepines and α-diazo carbonyl reagents. The [1,2]-Stevens rearrangement is general (61–93% yields) and can be extended to [3]ferrocenophanes; similar reactivity in favor of the products of ring expansion is obtained with these ferrocene derivatives (80–96% yields).

An unusual palladium hydride complex has been shown to be a competent catalyst in the isomerization of a variety of terminal and internal epoxides. The reaction displayed broad scope and synthetic utility. Experimental and theoretical evidence are provided for an unprecedented hydride mechanism characterized by two distinct enantio-determining steps. These results hold promise for the development of an enantioselective variant of the reaction.

This transformation tolerates a large variety of electronically different substituents on both reactive partners.

The first organocatalytic diastereo- and enantioselective domino Michael/aldol reaction of 3-halogeno-1,2-diones to α,β-unsaturated aldehydes has been achieved. This transformation tolerates a large variety of electronically different substituents on both reactive partners and allows the synthesis of challenging cyclopentanone derivatives with four contiguous stereogenic centers in excellent diastereoselectivities (>20:1 dr) as well as good yields (69–97%), and enantioselectivities (up to 94% ee).

The present manuscript describes a high-yielding enantioselective semipinacol transposition, initiated by an electrophilic iodination event. The title transformation makes use of the anionic phase-transfer catalysis (PTC) paradigm for chirality induction. Thus, when combined appropriately, the insoluble cationic iodinating reagent S9 and the lipophilic phosphoric acid L9 act as an efficient source of chiral iodine that performs the semipinacol transposition of strained allylic alcohols A(x) to β-iodo spiroketones B(x) in good yields and with high levels of diastereo- and enantio-induction. The product β-iodo spiroketones could be derivatized stereospecifically and without stereoerosion, giving rise to products inaccessible directly from a semipinacol rearrangement.

International audience; Herein, we discuss how, why, and when cascade complexation reactions produce stable, mononuclear, luminescent ternary complexes, by considering the binding of hexafluoroacetylacetonate anions (hfac(-)) and neutral, semi-rigid, tridentate 2,6-bis(benzimidazol-2-yl)pyridine ligands (Lk) to trivalent lanthanide atoms (Ln(III)). The solid-state structures of [Ln(Lk)(hfac)(3)] (Ln=La, Eu, Lu) showed that [Ln(hfac)(3)] behaved as a neutral six-coordinate lanthanide carrier with remarkable properties: 1) the strong cohesion between the trivalent cation and the didentate hfac anions prevented salt dissociation; 2) the electron-withdrawing trifluoromethyl substituents limited charge-neutralization and favored cascade complexation with Lk; 3) nine-coordination was preserved for [Ln(Lk)(hfac)(3)] for the complete lanthanide series, whilst a counterintuitive trend showed that the complexes formed with the smaller lanthanide elements were destabilized. Thermodynamic and NMR spectroscopic studies in solution confirmed that these characteristics were retained for solvated molecules, but the operation of concerted anion/ligand transfers with the larger cations induced subtle structural variations. Combined with the strong red photoluminescence of [Eu(Lk)(hfac)(3)], the ternary system Ln(III)/hfac(-)/Lk is a promising candidate for the planned metal-loading of preformed multi-tridentate polymers.

International audience; This work illustrates a simple approach for optimizing the lanthanide luminescence in molecular dinuclear lanthanide complexes and identifies a particular multidentate europium complex as the best candidate for further incorporation into polymeric materials. The central phenyl ring in the bis-tridentate model ligands L3-L5, which are substituted with neutral (X = H, L3), electron-withdrawing (X = F, L4), or electron-donating (X = OCH3, L5) groups, separates the 2,6-bis(benzimidazol-2-yl)pyridine binding units of linear oligomeric multi-tridentate ligand strands that are designed for the complexation of luminescent trivalent lanthanides, Ln(III). Reactions of L3-L5 with [Ln(hfac)3(diglyme)] (hfac- is the hexafluoroacetylacetonate anion) produce saturated single-stranded dumbbell-shaped complexes [Ln2(Lk)(hfac)6] (k = 3-5), in which the lanthanide ions of the two nine-coordinate neutral [N3Ln(hfac)3] units are separated by 12-14 Å. The thermodynamic affinities of [Ln(hfac)3] for the tridentate binding sites in L3-L5 are average (6.6 ≤ log(β(2,1)(Y,Lk)) ≤ 8.4) but still result in 15-30% dissociation at millimolar concentrations in acetonitrile. In addition to the empirical solubility trend found in organic solvents (L4 > L3 > L5), which suggests that the 1,4-difluorophenyl spacer in L4 is preferable, we have developed a novel tool for deciphering the photophysical sensitization processes operating in [Eu2(Lk)(hfac)6]. A simple interpretation of the complete set of rate constants characterizing the energy migration mechanisms provides straightforward objective criteria for the selection of [Eu2(L4)(hfac)6] as the most promising building block.

The axial connection of flexi- ble thioalkyls chains of variable length (n = 1-12) within the segmental bis-tri- dentate 2-benzimidazole-8-hydroxyqui- noline ligands (L12 Cn � 2H ) 2� provides amphiphilic receptors designed for the synthesis of neutral dinuclear lantha- nides helicates. However, the stoichio- metric mixing of metals and ligands in basic media only yields intricate mix- tures of poorly soluble aggregates. The addition of Ag I in solution restores classical helicate architectures for n = 3, with the quantitative formation of the discrete D3-symmetrical (Ln2Ag2- AL12 C3 � 2H )3) 2 + complexes at millimo- lar concentration (Ln = La, Eu, Lu). The X-ray crystal structure supports the formation of (La2Ag2(L12 C3 � 2H )3)- A2, which exists in the solid state as infinite linear polymers bridged by S- Ag-S bonds. In contrast, molecular dy- namics (MD) simulations in the gas phase and in solution confirm the ex- perimental diffusion measurements, which imply the formation of discrete molecular entities in these media, in which the sulfur atoms of each lipophil- ic ligand are rapidly exchanged within the Ag I coordination sphere. Turned as a predictive tool, MD suggests that this Ag I templating effect is efficient only for n = 1-3, while for n > 3 very loose interactions occur between Ag I and the thioalkyl residues. The subsequent ex- perimental demonstration that only 25 % of the total ligand speciation con- tributes to the formation of (Ln2Ag2(L12 C12 � 2H )3) 2 + in solution puts the bases for a rational approach for the design of amphiphilic helical complexes with predetermined molecu- lar interfaces.

Despite the recent emergence of a toolbox fitted with microscopic thermodynamic descriptors for predicting the stabilities and speciations of polynuclear complexes in solution, the discovery of novel or unusual type of metal-ligand assemblies in metallosupramolecular chemistry still often relies on serendipity. In order to highlight the novel perspectives offered by a rational exploitation of these thermodynamic parameters, the segmental bis-tridentate ligands L7 and L8 have been designed for providing effective molarities upon reaction with trivalent lanthanides, Ln(III), so small that the saturated binuclear triple-stranded helicates [Ln(2)(Lk)(3)](6+), which obey the well-respected principle of maximum site occupancy, cannot be detected in solution because of their deliberately planned instabilities. The hierarchical evolution of the effective molarities with an increasing number of ligand strands in these complexes indeed favors the formation of the alternative unsaturated single-stranded [Ln(2)(Lk)](6+) and double-stranded [Ln(2)(Lk)(2)](6+) complexes, whose relative speciations in solution depend on the nature of the binding sites introduced into the segmental ligand.

The replacement of terminal 2-benzimidazol-6-carboxypyridine (two internal rotational degrees of freedom) with 2-benzimidazol-8-hydroxyquinoline (one internal rotational degree of freedom) into segmental bis-tridentate ligands in going from L2 and [L3-2 H](2-) to [L12 b-2 H](2-) does not significantly affect the structures of the resulting binuclear lanthanide triple-stranded helical complexes [Ln(2)(L2)(3)](6+), [Ln(2)(L3-2 H)(3)], and [Ln(2)(L12 b-2 H)(3)] (palindromic helices, intermetallic contact distance approximately 9 A, helical pitch approximately 1.4 nm per turn). However, their thermodynamic assemblies are completely different in solution, as evidenced by the spectacular decrease of the effective concentrations by two orders of magnitude for [L12 b-2 H](2-). This key parameter in the [Ln(2)(L12 b-2 H)(n)] (n=2, 3) complexes is further abruptly modulated along the lanthanide series (Ln=La to Lu), which provides an unprecedented tool for 1) tuning the number of ligand strands in the final helicates, 2) selectively coordinating lanthanides in the various complexes, and 3) controlling the ratio of lanthanide-containing polymers over discrete assemblies.

Invited for the cover of this issue is the group of Emmanuel Terazzi at the University of Geneva, Switzerland. The cover image shows how single-stranded dinuclear lanthanide helicates (green) survive immersion into a drop of less polar solvent (e.g. CH2Cl2) and their eventual self-organization into a liquid-crystalline material.

A palladium-catalyzed intermolecular γ-arylation of γ-branched α,β-unsaturated aldehydes has been developed. The reaction allows congested quaternary centers to be forged on a remote position from the carbonyl group, affording a variety of products in high yield and with consistently high stereoselectivity using very low catalyst loadings. The synthetic utility of the products has been highlighted by a series of derivatizations and the potential of the method to be extended to remote ε-functionalization has been demonstrated.