The carbene or carbocationic nature of the intermediates in the gold-catalyzed cycloisomerization of 1,5-enynes can be revealed, depending on the ligands on the gold catalysts. Gold complexes with highly electron-donating ligands promote reactions that proceed via intermediates with carbene-like character, leading to products with a bicyclo[3.1.0]hexene skeleton. The intermediate cyclopropyl endo-gold carbenes formed in this cyclization have been trapped, for the first time, to give biscyclopropane derivatives in a reaction that proceeds in a concerted fashion, according to DFT calculations.

We report the first catalyst based on palladium for the reaction of CO2, alkene and a base to form sodium acrylate and derivatives. A mechanism similar to a previously reported Ni(0)-catalyst is proposed based on stoichiometric in situ NMR experiments, isolated intermediates and a parent palladalactone. Our palladium catalyst was applied to the coupling of CO2 with conjugated alkenes.

A heart of gold: Phenols can be obtained by the intermolecular reaction of furans with alkynes by using [AuIPr](+)A(-) catalysts (see scheme). 1,3-Diphenylisobenzofuran also reacts via a cyclopropyl gold carbene to selectively form 2,3-disubstituted indenes. (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; A = anion.).

The synthesis of sodium acrylate through catalytic carboxylation of ethylene with CO2 in the presence of a base is a reaction of high interest. To develop a more efficient and sustainable method to access this valuable acrylate monomer, we optimized the system in a one‐step homogeneous nickel‐ or palladium‐catalyzed reaction, without the need for stoichiometric amounts of an additional reducing agent. Suitable nontoxic solvents such as anisole instead of the previously reported tetrahydrofuran or chlorobenzene were found to lead to acrylate formation. In combination with appropriate phenolate bases, this could allow a rational process concept for a simple catalyst recycling, product separation, and base regeneration.

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