Sandra Olivero

Electrochemical intramolecular reductive cyclisation catalysed by electrogenerated Ni(cyclam)2

The intramolecular cyclisation of a series of o-halogenated aromatic compounds containing unsaturated side-chains has been developed using electrosynthesis, combined with organometallic catalysis by Ni(cyclam)Br2.

An Opportunity for Mg-Catalyzed Grignard-Type Reactions: Direct Coupling of Benzylic Halides with Pinacolborane with 10 mol % of Magnesium

Mg in catalytic amounts as the only metal permits the reductive coupling between benzyl halides and pinacolborane. HBpin acts both as an electrophile and as a reducing agent to regenerate an organomagnesium species in situ. An hydride oxidation mechanism is proposed on the basis of DFT calculations.

Electroreductive cyclisation of unsaturated halides catalysed by nickel macrocyclic complexes

Abstract The indirect electroreduction of unsaturated aliphatic halides using Ni(II) complexes as electron-transfer mediators is achieved in N,N′ -dimethylformamide by constant current electrolysis between a cathode and a sacrificial anode in a diaphragmless cell. Cyclic compounds are obtained in low to high yields in conditions that avoid the usual preparation using organotin reagents.

Biomimetic Cationic Polyannulation Reaction Catalyzed by Bi(OTf)3: Cyclization of 1,6-Dienes, 1,6,10-Trienes, and Aryl Polyenes

Nonactivated trienes and aryltrienes were cyclized into polycyclic compounds in good to excellent yields under bismuth triflate catalysis in a biomimetic fashion. The reaction showed broad applicability and allowed for the formation of functionalized bicyclic to tetracyclic structures from simple precursors in one pot. For some specific substrates, the cyclization was followed by a methyl shift as encountered in terpenoid biosynthesis.

Application of cooperative iron/copper catalysis to a palladium-free borylation of aryl bromides with pinacolborane.

A new cooperative copper/iron catalysis for the borylation of various aryl bromides with pinacolborane, at -10 °C, is reported. Use of the toxic, precious metal Pd is avoided. The mechanism of the protodebromination side reaction is discussed.

Intramolecular reductive cyclisations using electrochemistry: development of environmentally friendly synthetic methodologies

This review summarises electrochemical reductive intramolecular cyclisations, including transition-metal catalysed reactions. It presents some selected examples of organic halide electroreductions with further intramolecular coupling reactions, carbonyl group reductions with further coupling and intramolecular cyclisations involving electrogenerated bases.

NICKEL-CATALYSED ELECTROREDUCTIVE CLEAVAGE OF PROPARGYL COMPOUNDS

The selective reduction of propargyl esters and aryl ethers, involving the cleavage of the propargyl-oxygen bond, affords the corresponding carboxylic acids and phenols in good yields. The reaction proceeds through electrosynthesis combined with the catalysis by NiII-bipyridine complexes, under mild conditions.

Selectivity in the Tandem Cyclization – Carboxylation Reaction of Unsaturated Haloaryl Ethers Catalyzed by Electrogenerated Nickel Complexes

The electrochemical reduction of a series of 2-haloaryl ethers containing allyl and propargyl groups under CO2 allows the synthesis of benzofuranacetic acid derivatives. This novel intramolecular cyclization–carboxylation reaction is carried out in single-compartment cells and is catalyzed by [Ni(cyclam)Br2].

Mass spectrometric characterization of metal triflates and triflimides (Lewis superacid catalysts) by electrospray ionization and tandem mass spectrometry

Trifluoromethylsulfonate (triflate) and bis(trifluoromethylsulfonyl)imide (triflimide) salts, well-known Lewis acid catalysts, present some difficulty in their characterization. By using nitromethane as the solvent, useful electrospray mass spectra in positive and negative ion mode were obtained for salts of metals in oxidation states +2 and +3. In positive mode, addition of a strong Lewis base (triphenylphosphine oxide, TPPO), capable of displacing a triflate (TfO(-)) or a triflimide (Tf(2)N(-)) anion, is necessary for obtaining useful spectra. Under these conditions of solvent and added ligand, the most abundant ions were [M(2+)(A(-))(TPPO)(2)](+) or [M(3+)(A(-))(2)(TPPO)(2)](+) with A(-) = TfO(-) or Tf(2)N(-). The MS/MS spectra of these diagnostic ions provide additional analytical information. The breakdown curves, in the form of % dissociated as a function of the ion activation energy, offer a mean for investigating the bonding in these ions.

Nickel-catalysed electrochemical reductive deprotection of allyl ethers

The selective deprotection of a series of functionalized alkyl and aryl allyl ethers to the parent alcohols or phenols, under non-hydrolytic conditions, is effected by the combination of electrochemistry and catalysis by NiII–bipyridine complexes.