Development of New Gold (I)‐Catalyzed Carbocyclizations and their Applications in the Synthesis of Natural Products

Abstract

For many years, gold was considered inactive to catalyze organic transformations. In the last two decades, gold(I/III) complexes have emerged as efficient catalyst for the formation of C−O, C−N and C−C bonds. In particular, monomeric organogold complexes whose binding affinity for alkenes, allenes and alkynes opened new directions in organic synthesis. More recently, dimeric gold species were used as photocatalyst in light‐enabling processes. Taking advantage of the gold unique reactivity, we describe the development of novel transformations catalyzed by gold and their applications in the synthesis of natural products.

Excimer and Exciplex Formation in Gold(I) Complexes Preconditioned by Aurophilic Interactions

“…Thepioneering investigations of Che and co-workers into the use of photo-activated, phosphine-bridged, dinuclear gold(I) complexes (N)a so xidants or reductants,a nd finally as catalysts,for CÀCbond formation [186] have lately served as an impetus for other research groups to employ such weakly Au•••Au-bonded complexes as precatalytic mediators in photocatalysis.T he term "photoredox binuclear gold catalysis" now covers aw ide range of applications in preparative organic chemistry.M ajor contributions were independently made by the research groups of Barriault, Hashmi, and others. Them ost important results have been concisely reviewed by Barriault and co-workers, [227,228] and are not repeated in detail here.Avariety of reactions including C À Xb ond cleavage, C À Ca nd C À Nc ross-coupling,p inacol rearrangements,a nd even Heck-like additions were successfully catalyzed. The [Au I À ÀAu I ]* excimer fragment existing in al ong-lived triplet state appears as an active center upon irradiation of the reaction mixture with tunable light sources as proposed in the corresponding catalytic cycles.Applications in total synthesis ((AE)-triptolide in Barriaultsgroup; [229] pyrroloazocine indole alkaloids by Echavarren and co-workers [230] )a nd radical polymerization by Nzulu and co-workers [231] have convincingly illustrated the power and scope of the approach.…”

“…Major contributions were independently made by the research groups of Barriault, Hashmi, and others. The most important results have been concisely reviewed by Barriault and co‐workers, and are not repeated in detail here. A variety of reactions including C−X bond cleavage, C−C and C−N cross‐coupling, pinacol rearrangements, and even Heck‐like additions were successfully catalyzed.…”

Excimer‐ und Exciplex‐Bildung in durch aurophile Wechselwirkungen präkonditionierten Gold(I)‐ Komplexen

“…Wichtige Beiträge wurden unabhängig von den Forschungsgruppen von Barriault, Hashmi und anderen geleistet. Die wichtigsten Ergebnisse sind schon von Barriault und Mitarbeitern kurz und klar zusammengefasst worden und werden hier nicht im Detail wiederholt. Eine Vielzahl von Reaktionen wie C‐X‐Bindungsbruch, C‐C‐ und C‐N‐Kreuzkupplung, Pinakol‐Umlagerung und selbst Heck‐ähnliche Additionen wurden erfolgreich katalysiert.…”

Gold-Catalyzed Synthesis of Small Rings

“…In 1987, the first homogeneous gold-catalyzed addition of nucleophiles to alkynes was realized by the group of Utimoto using sodium tetrachloroaurate dihydrate. , One decade later, Teles et al and Tanaka et al demonstrated the possibility of activating alkynes using gold­(I) complexes. From that point, the field of gold­(I) catalysis started to gain momentum year after year and still today remains one of the most active areas of research in organometallic chemistry. , This comes as a consequence of the ability of gold­(I) complexes to activate π bonds in a very selective manner. − Its potential, attributed partially to relativistic effects, is illustrated by the wide molecular complexity − that can be built through the gold­(I)-catalyzed cycloisomerization of enynes (Scheme ). − …”