Aluminum-Catalyzed Intramolecular Vinylation of Arenes by Vinyl Cations.

This study addresses the challenges associated with vinyl cation generation, a process that traditionally requires quite specific counterions. Described herein is a novel intramolecular vinylation of arenes catalyzed by aluminum(III) chloride, utilizing practical conditions and readily available vinyl triflates derived from 2-aceto-3-arylpropionates. Comprehensive experimental data support diverse carbocycle synthesis, exemplified by indenes and higher analogues.

Squaramide/Li-Catalyzed Direct S1-Type Reaction of Vinyl Triflates with Difluoroenoxysilanes through Vinyl Cations.

Difluoromethylene-skipped enones have been readily obtained from arylvinyltriflates and aryldifluoroenoxysilanes. While these useful compounds are difficult to synthesize by the classical aldol/dehydration approach, the use of a squaramide/Li catalyst allows their direct formation via a vinyl carbocation paired with a weakly coordinating perfluorinated alkoxyaluminate. This strategy makes possible a reaction between a typically weak electrophile and a weak nucleophile.

A cyclic divalent N(I) species isoelectronic to carbodiphosphoranes.

The formation of a rare type of diphosphazenium cation is described. Its synthesis features a unique oxidative dealkylation of an iminophosphorane-phosphole by a silver(I) salt. DFT study of this compound reveals the low valent character of the N(I) center.

Transition structures for the oxy-ene reaction.

An overlooked pericyclic reaction between allyl alcohols and alkenes to form carbonyl compounds is analyzed. It combines the characteristic features of the Alder-ene reaction and of the oxy-Cope rearrangement. This oxy-ene reaction could be involved in biosynthetic pathways.

DFT Analysis into the Calcium(II)-Catalyzed Coupling of Alcohols With Vinylboronic Acids: Cooperativity of Two Different Lewis Acids and Counterion Effects.

The mechanism of the calcium-catalyzed coupling of alcohols with vinylboronic acids has been analyzed by means of density functional theory computations. This study reveals that the calcium and boron Lewis acids associate to form a superelectrophile able to promote a pericyclic group transfer reaction with allyl alcohols. With other alcohols, the two Lewis acids act synergistically to activate the OH functionality and trigger a Si reaction pathway.

Alkynophilicity of Group 13 MX Salts: A Theoretical Study.

The concept of alkynophilicity is revisited with group 13 MX metal salts (M = In, Ga, Al, B; X = Cl, OTf) using M06-2X/6-31+G(d,p) calculations. This study aims at answering why some of these salts show reactivity toward enynes that is similar to that observed with late-transition-metal complexes, notably Au(I) species, and why some of them are inactive. For this purpose, the mechanism of the skeletal reorganization of 1,6-enynes into 1-vinylcyclopentenes has been computed, including monomeric ("standard") and dimeric (superelectrophilic) activation.

Modular Synthesis of 9,10-Dihydroacridines through an -C Alkenylation/Hydroarylation Sequence between Anilines and Aryl Alkynes in Hexafluoroisopropanol.

9,10-Dihydroacridines are frequently encountered as key scaffolds in OLEDs. However, accessing those compounds from feedstock precursors typically requires multiple steps. Herein, a modular one-pot synthesis of 9,10-dihydroacridine frameworks is achieved through a reaction sequence featuring a selective -C alkenylation of diarylamines with aryl alkynes followed by an intramolecular hydroarylation of the olefin formed as an intermediate.

Correction: Bimolecular vinylation of arenes by vinyl cations.

Correction for 'Bimolecular vinylation of arenes by vinyl cations' by Zhilong Li et al., Chem. Commun.

On the Superior Activity of In(I) versus In(III) Cations Toward Alkylation of Anilines and Intramolecular Hydroamination of Alkenes.

An efficient --alkylation of unprotected anilines with a variety of styrenes and alkenes using a univalent cationic indium(I) catalyst is reported. Mechanistic studies revealed that the reaction likely proceeds via a tandem hydroamination/Hofmann-Martius rearrangement. The high compatibility between the cationic indium(I) complex and primary anilines led us to develop an In(I)-catalyzed hydroamination of alkenes using unprotected primary and secondary alkenylamines.

Alkaline-earth complexes with macrocyclic-functionalised bis(phenolate)s and bis(fluoroalkoxide)s.

The synthesis and structural features of several families of unsolvated molecular complexes of the heavy alkaline earths (Ae = calcium, strontium and barium) supported by bis(phenolate)s or bis(fluoroalkoxide)s are described. These dianionic, multidentate ligands are built around diaza-macrocycles that contain either five or six N- and O-heteroatoms. Several of these complexes have been characterised by X-ray diffraction crystallography.

Exploring the Limits of π-Acid Catalysis Using Strongly Electrophilic Main Group Metal Complexes: The Case of Zinc and Aluminium.

The catalytic activity of cationic NHC-Zn and NHC-Al (NHC=N-heterocyclic carbene) complexes in reactions that require the electrophilic activation of soft C-C π bonds has been studied. The former proved able to act as a soft π-Lewis acid in a variety of transformations. The benefit of the bulky IPr NHC ligand was demonstrated by comparison with simple ZnX salts.

Bimolecular vinylation of arenes by vinyl cations.

Styrene derivatives can be easily synthesized from vinyl triflates and arenes under mild reaction conditions, using [Li][Al(OC(CF))] as a catalyst and LiHMDS as a base. This transformation is likely to involve a vinyl cation intermediate as an electrophile, which is corroborated by DFT calculations, deuterium-labeling and other control experiments. The use of an inert weakly coordinating anion is a decisive factor in this bimolecular vinylation process.

Synthesis of Bridged Tetrahydrobenzo[b]azepines and Derivatives through an Aza-Piancatelli Cyclization/Michael Addition Sequence.

Herein, we report the preparation of bridged tetrahydrobenzo[b]azepines, which was accomplished through an aza-Piancatelli cyclization/Michael addition sequence in a one-pot fashion from readily available precursors. It is noteworthy that a general method to access these scaffolds was hitherto unprecedented. Additionally, the multifaceted aspects of this process have been exemplified through its application to the synthesis of 2-azabicyclo[3.

Synthesis of Medium-Sized Carbocycles by Gallium-Catalyzed Tandem Carbonyl-Olefin Metathesis/Transfer Hydrogenation.

The first examples of a catalytic tandem process involving a ring-closing carbonyl-olefin metathesis and a transfer hydrogenation are described. 1,4-Cyclohexadiene has been used as an H surrogate to reduce the cyclic alkenes formed after the metathesis step. The same cationic gallium(III) complex, [IPr·GaCl][SbF], performs the two steps with functional group tolerance.

Gallium-Catalyzed Scriabine Reaction.

γ-Aryl enol acetates are easily obtained from diacetoxy alkenes and electron-rich arenes at room temperature using GaCl as catalyst. The products can then be converted into β-aryl aldehydes. This method represents the first broadly applicable catalytic version of the Scriabine reaction.

Synthesis of 3-Substituted 3-Bromo-1-phenylallenes from Alkynylcycloheptatrienes.

A new method has been developed for the preparation of 3-bromo-1-phenylallenes from 7-alkynylcycloheptatrienes and N-bromosuccinimide. Trisubstituted bromoallenes were obtained at room temperature in moderate to excellent yields. Functionalization of the carbon-bromine bond via Pd- or Cu-catalyzed cross-coupling reactions easily provided substituted allenes.

Spatially encoded diffusion-ordered NMR spectroscopy of reaction mixtures in organic solvents.

Diffusion-ordered NMR spectroscopy (DOSY) is a powerful method for the analysis of mixtures. Classic DOSY methods require several minutes of acquisition, and we show here that DOSY experiments can be recorded in less than one second for the challenging case of solution mixtures in low-viscosity solvents. The proposed method relies on a spatial encoding of the diffusion dimension, for which convection-compensation and spectral-selection strategies are introduced.

Iron-Catalyzed Reductive Ethylation of Imines with Ethanol.

The borrowing hydrogen strategy has been applied to the ethylation of imines with an air-stable iron complex as precatalyst. This approach opens new perspectives in this area as it enables the synthesis of unsymmetric tertiary amines from readily available substrates and ethanol as a C building block. A variety of imines bearing electron-rich aryl or alkyl groups at the nitrogen atom could be efficiently reductively alkylated without the need for molecular hydrogen.

Revealing the Activity of π-Acid Catalysts using a 7-Alkynyl Cycloheptatriene.

A compound that isomerizes into distinct products depending on the particular Lewis acid or Brønsted acid catalyst used is disclosed. One product can only be obtained with the softest π-acids, such as Au, Pt, Ga, or In complexes. Another is formed only with harder π-acids incorporating Ag or Cu salts.

Catalytic Activity of Gold(I) Complexes with Hemilabile P,N Ligands.

Two new cationic dinuclear gold(I) complexes, [Au {μ(P,N)-5} ]X -in which X=NTf (7; Tf=trifluoromethanesulfonate) or SbF (8) and 2-(diphenylphosphanyl)benzonitrile (5) is a P,N-bridging donor-have been synthesized and structurally characterized. These air-stable species and their dimeric and polymeric analogues possessing 1'-(diphenylphosphanyl)-1-cyanoferrocene (1) as the bridging ligand, [Au {μ(P,N)-1} ](NTf ) and [Au{μ(P,N)-1}] [SbF ] , were used as precatalysts in various Au-mediated C-C and C-O bond-forming reactions. The reactivity of these complexes revealed the hemilabile nature of their P,N ligands.

Acid-catalysed intramolecular addition of β-ketoesters to 1,3-dienes.

1,3-Dienyl β-keto esters are cyclised into bicyclolactones using the Bi(OTf)/TfOH catalytic system. This reaction represents a rare case of simultaneous C-C and C-O bond formation at positions 1 and 3 of a 1,3-diene. Application to the synthesis of ramulosin is presented.

Synthesis, biological evaluation and molecular modeling studies on novel quinonoid inhibitors of CDC25 phosphatases.

The cell division cycle 25 phosphatases (CDC25A, B, and C; E.C. 3.

Calcium-Catalyzed Synthesis of Polysubstituted 2-Alkenylfurans from β-Keto Esters Tethered to Propargyl Alcohols.

An efficient synthesis of polysubstituted 2-alkenylfurans using Ca(NTf ) /KPF as a catalytic mixture is described. It is based on the cycloelimination of readily available propargyl alcohols tethered to β-keto esters under dry conditions to avoid competitive Meyer-Schuster rearrangement. The furan can be further functionalized in situ by a calcium-catalyzed Friedel-Crafts-type reaction with secondary and tertiary alcohols.

Stapled helical -OPE foldamers as new circularly polarized luminescence emitters based on carbophilic interactions with Ag(i)-sensitivity.

-Oligo(phenylene)ethynylenes (-OPEs) stapled with enantiopure 2,3-dihydroxybutane diethers have highly intense circular dichroism (CD) spectra and excellent circular polarized luminescence (CPL) responses ( values up to 1.1 × 10), which are consistent with homochiral helically folded structures. In the presence of Ag(i), a change in the CPL emission is observed, representing the first example of CPL active small organic molecular emitters, which can be modulated by carbophilic interactions in a reversible manner.

Non-Innocent Behavior of Substrate Backbone Esters in Metal-Catalyzed Carbocyclizations and Friedel-Crafts Reactions of Enynes and Arenynes.

On the basis of DFT computations and experimental results, we show that the presence of the ester group in the backbone of organic substrates can influence the mechanism of metal-catalyzed carbocyclization reactions. The non-innocent role of the ester functionality in lowering the activation barrier of the key step of the gallium- and indium-catalyzed cycloisomerization of 1,6-enynes is revealed. In the case of the gallium-catalyzed hydroarylation of arenynes, the esters in the tether can deprotonate the Wheland intermediate, thus avoiding more energetically demanding [1,3]- or [1,2]/[1,2]-H shifts.