Pd-catalyzed cascade carbopalladation-annulation reaction of 3-(2-iodobenzyl)-indoles into fused 6/5/7/6- and 6/5/5/6- heterocyclic systems

Rhodium(III)-Catalyzed C-H Cascade Annulation of Arylhydrazines with 2-Diazo-1,3-indandiones for the Synthesis of Tetracyclic Indeno[1,2-b]indoles

An efficient approach for the preparation of tetracyclic indeno[1,2-b]indoles via Rh(III)-catalyzed C-H cascade annulation between arylhydrazines and diazo indan-1,3-diones has been established. In addition, a series of indeno[1,2-b]indoles were obtained in up to 96% yield with a wide range of substrates and high functional group tolerance. Finally, the diverse transformations of the desired products demonstrate the synthetic utility and utilization of this protocol.

A Tandem Nucleophilic Aminopalladation and Carbene Insertion Sequence for Indole Fused Polycycles

An efficient tandem nucleophilic aminopalladation and carbene insertion sequence is described for the synthesis of indole fused polycycles. The reaction process provides a variety of substituted indeno[1,2-b]indoles in up to 99% yields.

Gusakov E, Bang DN, Tkachev VV, Tupaeva IO, Tran DL, Nguyen TV, Duong TN, Vu Dinh H, A. Krasnikova T, M. Aldoshin S, Minkin VI. New Reactions of Contraction of the o-Quinone Ring with the Formation of Derivatives of 2-(2-Indolyl)-cyclopenta[b]pyrrole-3,4-diones and Pyrindino[1,2-a]indoles: A Combined Experimental and Density Functional Theory Investigation

Derivatives of 2-(2-indolyl)-cyclopenta[b]pyrrole-3,4-diones and pyrindino[1,2-a]indoles were synthesized by a new reaction of contraction of the o-quinone ring, and their structures were investigated by X-ray crystallography and nuclear magnetic resonance spectroscopy. The mechanisms of the reactions were suggested based on density functional theory calculations of the critical parts of the potential energy surfaces.

Synthesis of selenated tetracyclic indoloazulenes via iodine and diorganyl diselenides

Herein, we report an efficient protocol for the synthesis of selenated tetracyclic indoloazulenes. The reaction of diorganyl diselenides with molecular iodine in dichloromethane leads to the in situ formation of organo selenenyl iodide. The synthesis of selenylated tetracyclic indoloazulenes through intramolecular cascade cyclization has been achieved via organo selenenyl iodide and bisindole at room temperature under metal-free conditions in good yields. All compounds were fully characterized by the FT-IR, HRMS, and ¹H, ¹³C and ⁷⁷Se NMR spectral data.

Palladium-Catalyzed [2 + 2 + 1] Annulation of Alkyne-Tethered Aryl Iodides with Diaziridinone: Synthesis of 3,4-Fused Tricyclic Indoles

A novel palladium-catalyzed [2 + 2 + 1] annulation of alkyne-tethered aryl iodides with diaziridinone was developed, leading to the formation of 3,4-fused tricyclic indoles. From a mechanistic standpoint, the formation of fused tricyclic indole scaffolds involved C,C-palladacycles, which were synthesized through the intramolecular reaction of aryl halides and alkynes. The cascade reaction described herein could be carried out with a broad range of substrates and provided various 3,4-fused tricyclic indoles with yields up to 98%.

Catalyst-free facile synthesis of polycyclic indole/pyrrole substituted-1,2,3-triazoles

A general and catalyst-free access to the fused polycyclic N-heterocycles via an intramolecular azide-alkene cascade reaction under mild reaction conditions has been developed. The reaction is applicable to both indole and pyrrole substrates, and a variety of substituents are tolerated. The entire sequence can be carried out in a one-pot operation. This methodology provides a sustainable and efficient access to a variety of novel polycyclic indole/pyrrole substituted-1,2,3-triazoles.

Pd-Catalyzed Annulation of 1-Halo-8-arylnaphthalenes and Alkynes Leading to Heptagon-Embedded Aromatic Systems

A palladium-catalyzed heptagon-forming annulation reaction between 1-halo-8-arylnaphthalene and diarylacetylene is reported. The reaction is promoted using a catalytic system comprised of Pd(OAc)₂ , moderately electron-deficient triarylphosphine P(4-ClC₆ H₄ )₃ , and Ag₂ CO₃ to afford benzo[4,5]cyclohepta[1,2,3-de]naphthalene derivatives in moderate to good yields, in preference to fluoranthene as a competing byproduct. Twofold annulation can also be achieved to access a novel heptagon-embedded polycyclic aromatic hydrocarbon compound.

Cascade reaction based synthetic strategies targeting biologically intriguing indole polycycles

In this review, cascade reaction based synthesis strategies delivering biologically intriguing indole polycycles are presented.

Synthesis of Indoles through Palladium-Catalyzed Three-Component Reaction of Aryl Iodides, Alkynes, and Diaziridinone

The three-component reaction of aryl iodides, alkynes, and diaziridinone is described. The reaction provides an innovative synthetic approach for indoles. The approach features high efficiency, broad substrate scope, and excellent regioselectivity. C, C-Palladacycles should act as the intermediates. The C, C-palladacycles are obtained from simple aryl halides and alkynes and then reacted with diaziridinone to afford indoles.

Palladium-catalyzed sequential three-component reactions to access vinylsilanes

The intermolecular silylation reaction of C,C-palladacycles obtained from aryl halides and alkynes has been developed.

Cobalt-Catalyzed, Aminoquinoline-Directed Functionalization of Phosphinic Amide sp2 C-H Bonds

In this paper, we introduce arylphosphinic acid aminoquinoline amides as competent substrates for cobalt-catalyzed sp² C-H bond functionalization. Specifically, the feasibility of their coupling with alkynes, alkenes, and allyl pivalate has been demonstrated. Reactions are catalyzed by simple Co(NO₃)₂ hydrate in ethanol or mixed dioxane/tBuOH solvent in the presence of Mn(OAc)₃·2H₂O additive, sodium pivalate, or acetate base and use oxygen from the air as an oxidant. Directing group removal affords ortho-functionalized P,P-diarylphosphinic acids.

Reactivity of alkynylindole-2-carboxamides in [Pd]-catalysed C–H activation and phase transfer catalysis: formation of pyrrolo-diindolones vs. β-carbolinones

[Pd]-Catalysed reaction of 3-alkynylindole-2-carboxamidesviaC–H activation leads to pyrrolodiindolones; in contrast, under phase-transfer catalysis, the same precursors afford β-carbolinones.

Palladium-catalysed decarboxylative nitrile insertion via C–H activation or self-coupling of indole-2-carboxylic acids: a new route to indolocarbolines and triindoles

Palladium catalysed decarboxylative nitrile insertion/dual C–H activation of indole carboxylic acids afforded indolocarbolines or triindoles in the absence of nitriles.

Cobalt-catalyzed, aminoquinoline-directed C(sp²)-H bond alkenylation by alkynes

A method for cobalt-catalyzed, aminoquinoline- and picolinamide-directed C(sp(2))-H bond alkenylation by alkynes was developed. The method shows excellent functional-group tolerance and both internal and terminal alkynes are competent substrates for the coupling. The reaction employs a Co(OAc)2⋅4 H2O catalyst, Mn(OAc)2 co-catalyst, and oxygen (from air) as a terminal oxidant.