Facile Synthesis of 1,2,3,4-Tetrahydro-β-carbolines by One-Pot Domino Three-Component Indole Formation and Nucleophilic Cyclization

Facile Access to Structurally Diverse Antimalarial Indoles Using a One-Pot A3 Coupling and Domino Cyclization Approach

A multistep and diversity-oriented synthetic route aiming at the A3 coupling/domino cyclization of o-ethynyl anilines, aldehydes and s-amines is described. The preparation of the corresponding precursors included a series of transformations, such as haloperoxidation and Sonogashira cross-coupling reactions, amine protection, desilylation and amine reduction. Some products of the multicomponent reaction underwent further detosylation and Suzuki coupling. The resulting library of structurally diverse compounds was evaluated against blood and liver stage malaria parasites, which revealed a promising lead with sub-micromolar activity against intra-erythrocytic forms of Plasmodium falciparum. The results from this hit-to-lead optimization are hereby reported for the first time.

Redox-Neutral and Atom-Economic Route to β-Carbolines via Gold-Catalyzed [4 + 2] Cycloaddition of Indolylynamides and Cyanamides

Gold(I)-catalyzed [4 + 2] cycloaddition of indolylynamides and cyanamides (aminonitriles) is an efficient redox-neutral and atom-economic route to diversely substituted 1,3-diamino-β-carbolines. The protocol operates under mild conditions (Ph₃PAuNTf₂ 5 mol %, DCE, 60 °C) with a good tolerance to functional groups (23 examples and yields up to 98%). The obtained β-carboline systems represent a versatile synthetic platform with modifiable substituents for successive functionalizations. Control experiments indicate the crucial role of both the nature of reactants and the identity of employed catalysts in the developed cycloaddition.

One-Pot Synthesis of Symmetrical and Asymmetrical 3-Amino Diynes via Cu(I)-Catalyzed Reaction of Enaminones with Terminal Alkynes

An economical and efficient protocol for the direct construction of amino skipped diynes through the Cu(I)-catalyzed reaction of enaminones and terminal alkynes has been described. Different kinds of symmetrical and asymmetrical 3-amino diynes could be obtained in up to 83% yield through a one-pot reaction under mild conditions.

A synthetic route to 1,4-disubstituted tetrahydro-β-carbolines and tetrahydropyranoindoles via ring-opening/Pictet–Spengler reaction of aziridines and epoxides with indoles/aldehydes

A route to 1,4-disubstituted tetrahydro-β-carbolines and tetrahydropyrano[3,4-b]indoles in high yields and stereoselectivity via S_N2-type ring opening/Pictet–Spengler reaction of aziridines and epoxides with indoles is described.

Pd/Cu Cocatalyzed Oxidative Tandem C-H Aminocarbonylation and Dehydrogenation of Tryptamines: Synthesis of Carbolinones

The Pd/Cu cocatalyzed oxidative tandem C-H aminocarbonylation and dehydrogenation was developed, affording carbolinones with molecular oxygen as the terminal oxidant. Natural product strychnocarpine and its derivatives were prepared conveniently using this strategy.

Recyclable Cu/C3N4 composite catalyzed AHA/A3 coupling reactions for the synthesis of propargylamines

The heterogeneous Cu/C₃N₄ catalyst was found to be efficient for the synthesis of propargylamines using a three-component coupling reaction of alkynes, CH₂Cl₂ and amines (AHA) without additional base. Moreover, the catalyst also showed highly catalytic activity in the synthesis of C1-alkynylated tetrahydroisoquinolines (THIQs) via an A³ reaction of alkynes, aldehydes and THIQ. The Cu/C₃N₄-catalyzed multicomponent reactions exhibited good functional group tolerance in most examples. Furthermore, the easily prepared Cu/C₃N₄ catalyst could be recovered and reused conveniently over 5 times without losing catalytic activities.

Recyclable Cu/C₃N₄ composite, a highly efficient catalyst for the synthesis of propargylamines via an AHA/A³ reaction.

Rhodium(ii)-catalyzed intramolecular annulation of 1-sulfonyl-1,2,3-triazoles with indoles: facile synthesis of functionalized tetrahydro-β-carbolines

A novel rhodium(ii)-catalyzed intramolecular annulation of 1-sulfonyl-1,2,3-triazoles with indoles has been developed, which enables the facile synthesis of various 4-functionalized tetrahydro-β-carbolines and relevant scaffolds from readily available starting materials.

Bioglycerol-derived carbon−SO3H as a recyclable catalyst for the synthesis of tetrahydro-β-carbolines

A variety of aldehydes undergo smooth coupling with N-tosyltryptamine in the presence of carbon−SO3H in ethanol at 80 °C to furnish the corresponding tetrahydro-β-carbolines in excellent yields with high selectivity. The coupling of tryptamine with isatins affords the respective spiro-tetrahydro-β-carbolines in good yields. The use of a recyclable solid acid catalyst makes this method simple, convenient, and cost-effective.

Copper-catalyzed annulation of α-substituted diazoacetates with 2-ethynylanilines: the direct synthesis of C2-functionalized indoles

Copper-catalyzed direct annulation of α-substituted diazoacetates with 2-ethynylanilines leading to C2-functionalized indoles was achieved under mild reaction conditions. The C2-(carboxylate methyl) substituted indoles were obtained in moderate to high yields.

Gold-catalyzed three-component annulation: efficient synthesis of highly functionalized dihydropyrazoles from alkynes, hydrazines, and aldehydes or ketones

Polysubstituted dihydropyrazoles were directly obtained by a gold-catalyzed three-component annulation. This reaction consists of a Mannich-type coupling of alkynes with N,N'-disubstituted hydrazines and aldehydes/ketones followed by intramolecular hydroamination. Cascade cyclization using 1,2-dialkynylbenzene derivatives as the alkyne component was also performed producing fused tricyclic dihydropyrazoles in good yields.

Ruthenium-catalyzed γ-carbolinium ion formation from aryl azides; synthesis of dimebolin

A range of γ-carbolines were produced stereoselectively from ruthenium(III)-catalyzed reactions of 3-pyridyl substituted aryl azides. Other catalysts and conditions were neither as selective nor as high-yielding. This method was used to synthesize dimebolin in a concise and efficient manner.

Microwave multicomponent synthesis

In the manner that very important research is often performed by multidisciplinary research teams, the applications of multicomponent reactions involving the combination of multiple starting materials with different functional groups leading to the higher efficiency and environmentally friendly construction of multifunctional/complex target molecules is growing in importance. This review will explore the advances and advantages in microwave multicomponent synthesis (MMS) that have been achieved over the last five years.