One‐Pot Gold‐Catalyzed Synthesis of Azepino[1,2‐a]indoles

Abstract

Als außergewöhnlich effektiver Katalysator für die Eintopfsynthese tricyclischer Azepinoindole in einer neuartigen Kaskadenreaktion erwies sich ein Komplex aus Gold(I) und einem N‐heterocyclischen Carben (IPr=1,3‐Di(isopropylphenyl)imidazol‐2‐yliden). Einfach verfügbare Substrate, hohe Chemoselektivität, gute Ausbeuten und Wasser als einziges stöchiometrisches Begleitprodukt sind einige der Hauptvorteile dieser Methode.

Gold(I)‐Catalyzed Cycloisomerization of ortho‐(Propargyloxy)arenemethylenecyclopropanes Controlled by Adjacent Substituents at Aromatic Rings

“…On the basis of the above resultsand previously reported literature, plausible mechanisms for these reactions are shown in Scheme6.I nC ycle I, the gold complex initially coordinates with the triple bond of substrate 1a to give intermediate A, which affords vinyl gold [17] intermediate B containing af ivemembered ring through cyclization. Next, ring enlargement of intermediate B affords intermediate C,w hich forms intermediate D by intramolecular cyclopropanation [18] and methylenecyclopropane migration via three-membered ring transition state TS3 (Scheme 7).…”

“…On the basis of the above resultsand previously reported literature, plausible mechanisms for these reactions are shown in Scheme6.I nC ycle I, the gold complex initially coordinates with the triple bond of substrate 1a to give intermediate A, which affords vinyl gold [17] [18] and methylenecyclopropane migration via three-membered ring transition state TS3 (Scheme 7). Finally,i ntermediate D undergoes dehydro-aromatization and reprotonation to afford 2a with regeneration of the gold(I) catalyst.…”

Silver‐Catalyzed Cross‐Coupling of Propargylic Alcohols with Isocyanides: An Atom‐Economical Synthesis of 2,3‐Allenamides

“…[12] We envisaged, thereafter, that utilization of propargylic alcohols, instead of simple alkynes, in this silver-catalyzed protocol might lead to a different reaction pattern because of the close proximity of a highly reactive hydroxyl group to the alkyne unit. [2] Delightfully, our experimental results confirmed this hypothesis and disclosed an unprecedented b-CÀC coupling and oxygen transposition of propargylic alcohols with isocyanides, thereby providing a novel route to a variety of synthetically valuable 2,3-allenamides ( Figure 1). [13] To the best of our knowledge, this represents the first example of a CÀC coupling reaction between propargylic alcohols and isocyanides.…”

“…Propargylic alcohols are very useful bifunctional building blocks and the close proximity of the hydroxyl group to the CC bond provides these molecules with the potential to undergo reactions that are not possible with the corresponding alkynes. [2] The transition-metal-catalyzed CÀC bond formation at the aor b-carbon atom of propargylic alcohols, along with oxygen transposition by cross-coupling with a coupling partner, is especially striking because it constitutes a powerful strategy towards oxygen-functionalized unsaturated compounds. [3][4][5] However, such a useful synthetic strategy remains underexploited so far.…”

Synthesis of 1H‐Pyrrolo[1,2‐a]indoles via Lewis Acid‐Catalyzed Annulation of Propargylic Alcohols with 2‐Ethynylanilines

“…These types of motifs are valuable starting points and are abundant in biologically active natural products and functional materials. [5] Polycyclic indoles represent an important class of fused heterocycles, and are the core structural motifs of a wide array of agrochemicals and pharmaceuticals. Among them, 1H-pyrrolo[1, 2-a]indoles are of great interest in organic synthesis and medicinal chemistry due to their significant biological and pharmacological activities, such as antitumor, antimalarial, antiviral, and anti-implantation activities.…”