Construction of Tricyclic Nitrogen Heterocycles by a Gold(I)‐Catalyzed Cascade Cyclization of Allenynes and Application to Polycyclic π‐Electron Systems

Abstract

An ovel approach to the direct construction of tricyclic nitrogen heterocycles based on gold-catalyzed cascade cyclization of aminoallenynes is described. The expected biscyclization reaction of hydroxyisobutyryl-protected aminoallenynes was efficiently promoted by ac atalytic amount of BrettPhosAuNTf 2 in the presence of iPrOH to produce 1,2dihydrobenzo[cd]indole derivatives in good yields.W hen the reaction was combined with Friedel-Crafts acylation or palladium-catalyzed N-arylation, the resulting tricyclic products were efficiently converted into nitrogen-containing polycyclic aromatic compounds (N-PACs) with highly conjugated p-electron systems.Anewly obtained hexacyclic indolium salt showed characteristic concentration-dependent absorption and emission properties. Scheme 1. Gold(I)-catalyzed reactions of diynes and related compounds proceedingvia vinyl cation intermediates.

Advancements in Gold‐Catalyzed Cascade Reactions to Access Carbocycles and Heterocycles: An Overview

“…Fukazawa and Ohno group reported a gold‐catalyzed cascade cyclization of aminoallenynes 7 , a unique method for the direct construction of tricyclic nitrogen heterocycles (Scheme 3). [32] 5 mol% of BrettPhosAuNTf 2 was effectively used to promote the desired biscyclization reaction of hydroxyisobutyryl‐protected aminoallenynes 7 in the presence of i PrOH, yielding 1,2‐ dihydrobenzo[ c,d ]indole derivatives 8 in 46–82 %. The resultant tricyclic products were effectively transformed into nitrogen‐containing polycyclic aromatic compounds ( N‐PACs ) with strongly conjugated π ‐electron systems when the procedure was coupled with Friedel‐Crafts acylation or palladium‐catalyzed N ‐arylation.…”

Gold(I)‐Catalyzed Bis‐Cyclization of Allenynes for the Synthesis of Strained and Planar Polycyclic Compounds

“…[4] We also found that the vinyl cation species can be trapped by a nitrogen nucleophile to produce tricyclic fused indoles 4 and pyrrolonaphthalenes 5 (Scheme 2B). [5] We next envisaged that the intramolecular arylation of vinyl cations might produce highly π-conjugated molecules with a strained structure.…”

Gold(I)-Catalyzed Benzylic C(sp3)-H Functionalizations: Product Bifurcation towards Indole[a]- and [b]-Fused Polycycles

“…[63] In our ongoing endeavors in reaction development using gold catalysis, [42][43][44][45][46][47] we previously reported the synthesis of acenaphthenes 2, which can be rationalized by a 1,5-hydride shift on a vinyl cationic gold complex A generated from allenynes 1 (Scheme 1B). [64,65] From this vantage point, we envisioned that a 1,5-hydride shift leading to electrophilic α-imino gold carbene functionalization should also be conceivable in gold-catalyzed electrophilic C-H functionalization, leading to fused indoles such as 4 (Scheme 1C), which often exhibit biologically intriguing properties. [21] Herein we present our research to show that alkynylated arylazides are suitable substrates for gold-catalyzed cascade cyclizations to form indeno[b]-type fused indoles 4 via a 1,5-hydride shift on α-imino gold carbenes and C-cyclization.…”