A new, one-step route to N-heterocyclic oxo-carbene complexes (NHOCs), representatives of chemo-switchable NHC complexes, is reported. This simple procedure provides an easy access to gold, palladium and platinum complexes of these ligands.

Readily available phenols can be converted into substituted aryl alkynyl ethers, which react with an N‐oxide as an oxidant and catalytic amounts of a Brønsted acid to provide benzofuranones. If non‐terminal alkynyl ethers are applied, a 1,2‐hydride shift takes place and phenyl acrylates are obtained. Thus activated alkynes can serve as α‐oxy carbene precursors even in the absence of a metal catalyst.

Different arylgold(i), one alkynylgold(i), and one vinylgold(i) triphenylphosphane complexes were subjected to electrophilic halogenation reagents. With N-chlorosuccinimid, N-bromosuccinimid, and N-iodosuccinimid as well as the Barluenga reagent, selectively halogenated compounds were obtained. Trifluoroacetic acid, as a source of protons, leads to a clean protodeauration. With N-fluorobenzenesulfonimide or Selectfluor, exclusively a homocoupling was observed. For the precursor of the vinylgold(i) complex, a similar oxidative coupling could be induced by gold(iii) chloride. Reactions with silicon or tin electrophiles failed.

In am odular template synthesis,unsaturated NHC complexes of gold, palladium andp latinum were synthesizedf rom simplem etal salts,i sonitriles and aminesw ith acetal or ketal groups.U pon the addition of aminesw ith tethereda cetal or ketal moieties to the metal-activated isonitrile,f irst nitrogen acyclic carbene (NAC)c omplexes are formed. These undergo ring closure and elimination to the unsaturated NHC complexes upon addition of acid. This simples trategyo pens an attractive and fast approach to NHC complexes of gold, palladium and platinum. Them odular approach allowsafast modification and is well-suited for the synthesiso fu nsymetrically and symmetricallys ubstituted unsaturated NHC complexes.Scheme 1. NHC-Synthesis via metal isonitrile precursors; left:i ntermolecular process,r ight:i ntramolecular process.

Under the conditions of dual activation catalysis with oxygen nucleophiles, β‐substituted naphthalenes were obtained from 1,2‐diethinyl arenes. Mechanistic studies, which include isotope labeling experiments, support that dual activation leads to β‐substituted naphthalenes, whereas α‐naphthalenes are formed by π activation only, and no gold acetylide or dual activation is involved in the formation of the α‐substituted products. Additional experiments on substrates that led to dibenzopentalenes support these mechanistic insights.

The gold-catalyzed conversion of allyl-(ortho-alkynylphenyl)methyl ethers was investigated, and allylated isochromenes were obtained. An optimization of the catalysis conditions with respect to different phosphane and carbene ligands on gold, different counterions, and different solvents was conducted. Subsequently, the scope and limitations of this reaction were investigated with 21 substrates. The mechanistic studies show an allylic inversion, as supported by NMR data and an X-ray crystal structure analysis, as well as an intermolecular reaction, as determined by crossover experiments. There is no competition of protodeauration even in the presence of water. All these observations differ from other related conversions and clearly indicate product formation by a [3,3]sigmatropic rearrangement in the step forming the new C-C bond.

The gold(I)‐catalyzed reaction of allyl 2‐en‐4‐ynyl ethers provides stereoselectively (Z)‐1,3,6‐trienes with an acyl substitutent in the 4‐position. The reaction proceeds through an oxygen transfer along the chain and a clean allylic inversion. This complements the preceding work by Gagosz, who obtained furan derivatives in his investigation of similar substrates with terminal alkynyl groups.10, 16 The only drawback of this mechanistically new pathway is the instability of the products under the reaction conditions, which sometimes prevents their isolation in high yields.

Aus leicht zugänglichen Phenolen wurden substituierte Aryl‐Alkinyl‐Ether hergestellt, deren Umsetzung mit einem N‐Oxid als Oxidationsmittel in Gegenwart katalytischer Mengen einer Brønsted‐Säure effektiv Benzofuranone ergibt. Nichtterminale Alkinylether durchlaufen dabei eine 1,2‐Hydrid‐Verschiebung, die zu Phenylacrylaten führt. Somit können aktivierte Alkine auch in Abwesenheit von Metallkatalysatoren als α‐Oxycarben‐Vorstufen genutzt werden.