Reactions of Cationic Gold(I) with Allenoates: Synthesis of Stable Organogold(I) Complexes and Mechanistic Investigations on Gold‐Catalyzed Cyclizations

Abstract

The reaction of allenoates with cationic gold(I)-generated in situ from a phosphine gold chloride and a silver salt-formed unusual, room temperature stable vinyl gold(I) lactones under very mild conditions. The scope and limitations for the synthesis of this novel organogold complex was investigated. DFT calculations on the highest occupied molecular orbitals (HOMOs) of allenoates and the natural bond orbital (NBO) charge densities provided an explanation for the limitations. A plausible mechanism for its formation was proposed based on in situ (1)H and (31)P NMR spectroscopic analyses. Controlled experiments for the cleavage of the gold-carbon bond by electrophiles indicated that this vinyl gold(I) complex is the likely intermediate in the gold-catalyzed reaction of carbon-carbon multiple bonds.

Gold‐Catalyzed Intramolecular Oxidative Cross‐Coupling of Nonactivated Arenes

“…In a control experiment performed with AuCl (5 mol %) in acetonitrile, but omitting Selectfluor, compound 4 a was formed as the only product after 6 days (Scheme 2). [6,7] The formation of 2 a from 1 a, a new addition to the list of gold-catalyzed oxidative cross-coupling reactions reported to date, [4,5,8] is a challenging operation. Under the same reaction conditions, but with PtCl 2 , CuOAc, H 2 SO 4 , or AgOTf as the catalyst, 2 a and 3 a were not observed and with PdA C H T U N G T R E N N U N G (OAc) 2 (5 mol %) the dimers 3 a were formed as the only products with no trace of 2 a.…”

Pd(0)/Au(i) redox incompatibilities as revealed by Pd-catalyzed homo-coupling of arylgold(i)-complexes

“…15 Unfortunately, attempts to couple complexes A 16 and B 17 (Fig. 1) and TolOTf with various Pd-catalysts failed.…”

Elementary Steps in Gold Catalysis: The Significance of gem‐Diauration

“…Only recently have selected examples of alkenylgold species bearing a vicinal heteroatom substituent X been structurally characterized (see Scheme 1). [4][5][6][7] By considering the isolobal relationship between a proton and a LAu + fragment, [8] however, one may speculate that the catalyst itself could also (reversibly) react with C to give complexes of type E; this pathway might seriously compete with protodeauration given the affinity of the carbophilic late transition metal to p bonds. [1] A recent report by GagnØ and co-workers lent credence to this notion.…”