Stereoselective cis -Vinylcyclopropanation via a Gold(I)-Catalyzed Retro-Buchner Reaction under Mild Conditions

A highly stereoselective gold(I)-catalyzed cis-vinylcyclopropanation of alkenes has been developed. Allylic gold carbenes, generated via a retro-Buchner reaction of 7-alkenyl-1,3,5-cycloheptatrienes, react with alkenes to form vinylcyclopropanes. The gold(I)-catalyzed retro-Buchner reaction of these substrates proceeds by simple heating at a temperature much lower than that required for the reaction of 7-aryl-1,3,5-cycloheptatrienes (75 °C vs 120 °C). A newly developed Julia−Kocienski reagent enables the synthesis of the required cycloheptatriene derivatives in one step from readily available aldehydes or ketones. On the basis of mechanistic investigations, a stereochemical model for the cis selectivity was proposed. An unprecedented gold-catalyzed isomerization of cis– to trans-cyclopropanes has also been discovered and studied by DFT calculations

Strategies for the Synthesis of Higher Acenes

The outstanding performance of pentacene-based molecules in molecular electronics, as well as the predicted en- hanced semiconducting properties of extended acenes, have stimulated the development of new synthetic methods and functionalization strategies for the preparation of stable and soluble acenes larger than tetracene with the aim of obtaining improved functional materials

Ready Access to the Echinopine s Skeleton via Gold(I) – Catalyzed Alkoxycyclization s of Enynes

The [3,5,5,7] tetracyclic skeleton of echinopines has been stereoselectively accessed through a gold(I)-catalyzed alkoxycyclization of cyclopropyl-tethered 1,6-enynes. The key bicycle[4.2.1]nonane core of the enyne precursors was readily assembled by means of a Co-catalyzed [6+2] cycloaddition. Furthermore, the attempted alkoxycyclization of 1,5-enyne substrates revealed an uncovered cyclopropyl rearrangement that gives rise to [3,6,5,7] tetracyclic structures

Intriguing mechanistic labyrinths in gold(I) catalysis

Many mechanistically intriguing reactions have been developed in the last decade using gold(I) as catalyst. Here we review the main mechanistic proposals in gold-catalysed activation of alkynes and allenes, in which this metal plays a central role by stabilising a variety of complex cationic intermediates

Enantioselective Total Synthesis of (-)-Nardoaristolone B via a Gold(I)-Catalyzed Oxidative Cyclization

The first enantioselective total synthesis of (−)-nardoaristolone B is accomplished by the implementation of an enantio- and diastereoselective copper(I)-catalyzed conjugate addition/enolate trapping sequence and a gold(I)-catalyzed oxidative cyclization (intermolecular oxidant), employed for the first time in total synthesis

Hydroacenes made easy by gold(I) catalysis

A novel strategy for the synthesis of partially saturated acene derivatives has been developed based on a AuI-catalyzed cyclization of 1,7-enynes. This method provides straightforward access to stable polycyclic products featuring the backbone of the acene series, up to nonacene

Synthesis of (-)-Cannabimovone and Structural Reassignment of Anhydrocannabimovone through Gold(I)-Catalyzed Cycloisomerization

The first total synthesis of cannabimovone from Cannabis sativa and anhydrocannabimovone was achieved by means of a highly stereoselective gold(I)-catalyzed cycloisomerization. The results led to reassignment of the structure of anhydrocannabimovone

Rationale for the sluggish oxidative addition of aryl halides to Au(I)

The oxidative addition of Csp2–Br or Csp2–I bonds to gold(I) does not take place even under very favorable intramolecular conditions that could form five- or six-membered gold(III) metallacycles. DFT calculations reveal that although this process could be feasible thermodynamically, it is kinetically very sluggish

Gold(I) Carbenoids: On-Demand Access to Gold(I) Carbenes in Solution

Chloromethylgold(I) complexes of phosphine, phosphite, and N-heterocyclic carbene ligands are easily synthesized by reaction of trimethylsilyldiazomethane with the corresponding gold chloride precursors. Activation of these gold(I) carbenoids with a variety of chloride scavengers promotes reactivity typical of metallocarbenes in solution, namely homocoupling to ethylene, olefin cyclopropanation, and Buchner ring expansion of benzene

Broad scope gold(I)-catalysed polyenyne cyclisations for the formation of up to four carbon–carbon bonds

The cyclisation of 1,5-enynes containing alkenes, arenes, heteroarenes, and hydroxyl groups to form polycyclic compounds has been achieved with a cationic dicyclohexylphosphinobiphenyl gold(I) complex as catalyst under mild conditions and with low catalyst loadings. The polycyclisation has been extended to the simultaneous formation of up to four carbon-carbon bonds in bioinspired transformations