Photosensitizer‐Free Visible‐Light‐Mediated Gold‐Catalyzed 1,2‐Difunctionalization of Alkynes

Abstract

Under visible-light irradiation, the gold-catalyzed intermolecular difunctionalization of alkynes with aryl diazonium salts in methanol affords a variety of α-aryl ketones in moderate to good yields. In contrast to previous reports on gold-catalyzed reactions that involve redox cycles, no external oxidants or photosensitizers are required. The reaction proceeds smoothly under mild reaction conditions and shows broad functional-group tolerance. Further applications of this method demonstrate the general applicability of the arylation of a vinyl gold intermediate instead of the commonly used protodemetalation step. This step provides facile access to functionalized products in one-pot processes. With a P,N-bidentate ligand, a stable aryl gold(III) species was obtained, which constitutes the first direct experimental evidence for the commonly postulated direct oxidative addition of an aryl diazonium salt to a pyridine phosphine gold(I) complex.

Photopromoted Entry to Benzothiophenes, Benzoselenophenes, 3H‐Indoles, Isocoumarins, Benzosultams, and (Thio)flavones by Gold‐Catalyzed Arylative Heterocyclization of Alkynes

“…The detected regiochemistry of both ring closures (6-endo oxy-and thia-cyclizations) is in agreement with the results of Schemes 9 and 10. Despite that Hashmi [14] and Shi [15] have independently shown that no photoredox catalysts are required for related reactions, a control experiment verified that our reactions operates through [Ru(bpy)3](PF6)2 photoredox. Indeed, starting either from 1a-Si-SMe or 4a-Si no reaction occurred in the absence of the photosensitizer.…”

Visible light-induced transition metal-catalyzed transformations: beyond conventional photosensitizers

“…38 Blue light irradiation of aryl diazonium salts and internal alkynes in the presence of Au(I) catalyst and methanol generated the α -arylated ketone products in good yields. Using other light sources, such as CFLs or UVA lamps, led to lower efficiency.…”

Gold‐katalysierte 1,2‐Difunktionalisierung von Alkinen mit sichtbarem Licht ohne zusätzlichen Photosensibilisator

“…Die Struktur von 7 wurde zweifelsfrei über EinkristallRçntgenstrukturanalyse bestätigt (Schema 5, rechts). [13] Verglichen mit den bekannten Prozeduren, die die Kombination einer oxidativen Addition und einer Tr ansmetallierung unter harschen Bedingungen nutzen, [14] stellt dies einen eher leicht [15] die über die elektrophile Aryl-Au III -Zwischenstufe als Katalysator initiiert wird, gefolgt von der reduktiven Eliminierung zur zusätzlichen C-C-Bindung.A uf Basis der existierenden Berichte zur Gold(III)-katalysierten Sonogashira-Kreuzkupplung, [4c] hofften wir, als nächstes eine Tandem-Kreuzkupplung/Difunktionalisierung mit einem terminalen Alkin als Edukt zu verwirklichen. Die Umsetzung von Phenylacetylen 8a mit 5¾quiv.…”