FeCl3·6H2O-Catalyzed Alkenylation of Indoles with Aldehydes

Relevant Developments in the Use of Three-Component Reactions for the Total Synthesis of Natural Products. The last 15 Years

Multicomponent reactions (MCRs) offer a highly useful and valuable strategy that can fulfill an important role in synthesizing complex polysubstituted compounds, by simplifying otherwise long sequences and increasing their efficiency. The total synthesis of selected natural products employing three-component reactions as their common strategic MCR approach, is reviewed on a case-by-case basis with selected targets conquered during the last 15 years. The revision includes detailed descriptions of the selected successful sequences; relevant information on the isolation, and bioactivity of the different natural targets is also briefly provided.

Catalyst-Switchable Divergent Synthesis of Bis(indolyl)alkanes and 3-Alkylated Indoles from Styrene Oxides

A novel and effective Brønsted acid-catalyzed chemoselective synthesis of bis(indolyl)alkanes and 3-alkyl indoles is reported. The selectivity of two significant indole derivatives is attained by allowing the same substrates to go through divergent reaction routes catalyzed by different catalysts. Furthermore, this mild approach is applicable to a wide range of substrates and has high efficacy in large-scale reactions. A plausible mechanism is provided based on the control experiments and spectroscopic studies.

Efficient Synthesis of C3-Alkylated and Alkenylated Indoles via Manganese-Catalyzed Dehydrogenation

The catalytic dehydrogenation of alcohols is essential for the sustainable production of valuable products. This provids a new strategy for green organic synthesis in chemical industries. Herein, we describe a manganese-based catalytic system that enables the efficient synthesis of C3-alkylated indoles from benzyl alcohols and indoles via the borrowing hydrogen process. Furthermore, dehydrogenative coupling of 2-arylethanols and indoles yields C3-alkenylated indoles. Meanwhile, reacting 2-aminophenethanol instead of indoles can also obtain the corresponding indole products with high selectivity under the same conditions.

Short Total Synthesis of (±)-Gelliusine E and 2,3'-Bis(indolyl)ethylamines via PTSA-Catalyzed Transindolylation

A first and short total synthesis of the marine sponge 2,3'-bis(indolyl)ethylamine (2,3'-BIEA) alkaloid (±)-gelliusine E was performed in both a three-step divergent approach and a one-pot three-component approach with an overall yield of up to 58%. A key feature of the novel strategy is PTSA-catalyzed transindolylation of the readily synthesized 3,3'-BIEAs with tryptamine derivatives. The structure of the isolated natural product is revised as protonated (±)-gelliusine E (4'). By design, this modular route allows the rapid synthesis of other members of the 2,3'-BIEA family, for example, (±)-6,6'-bis-(debromo)-gelliusine F and analogues with step economy, operational simplicity, and reduced waste. Furthermore, their cytotoxicity in breast cancer cells was investigated.

FeCl3·6H2O as a Mild Catalyst for Nucleophilic Substitution of Symmetrical Bis(indoyl)methanes

In this paper, unsymmetrical bis(indolyl)methane (BIM) and 3-alkylindole derivatives are smoothly synthesized from symmetrical BIMs with a variety of nucleophiles including heteroaromatic/aromatic compounds, allylsilane and alkynylsilane. FeCl₃·6H₂O is found to be a mild and highly effective catalyst for this nucleophilic substitution reaction in which N-methyl-2-phenylindole behaves as a good leaving group in the C_sp³-C_sp² bond cleavage reaction. The operational ease, nonexpensive and environmentally friendly catalyst, mild reaction conditions, broad functional group tolerance, and scalability of this reaction strategy are advantages of the present procedure.

Organic synthesis with the most abundant transition metal–iron: from rust to multitasking catalysts

The promising aspects of iron in synthetic chemistry are being explored for three-four decades as a green and eco-friendly alternative to late transition metals. This present review unveils these rich iron-chemistry towards different transformations.

Cu/Pd-Catalyzed chemoselective synthesis of C-3 dicarbonyl indoles and bis(indolyl)alkanes from aldehydes and indoles

A novel Cu/Pd-catalyzed chemoselective synthesis of C-3 dicarbonyl indoles and bis(indolyl)alkanes from aldehydes and indoles has been achieved, which has good substrate universality and high efficacy on large-scale.

Rh(iii)-Catalyzed regio- and stereoselective bisindolylation of vinyl acetate: an efficient approach toward (E)-1,2-bis(2-indolyl)ethenes

An efficient Rh(iii)-catalyzed regio- and stereoselective cross-coupling between vinyl acetate andN-(2-pyridiyl)indoles providing a series of (E)-2,2′-bis(indolyl)ethenes has been developed.

Catalyst-Controlled Chemodivergent Modification of Indoles with 2-Furylcarbinols: Piancatelli Reaction vs Cross-Dehydrative Coupling Reaction

A divergent synthetic strategy to functionalize the indole nucleus with readily available 2-furylcarbinols was developed. It was found that the 3-(4-oxo-2-cyclopentenyl)indoles were obtained in moderate to good yields (up to 89%) through Piancatelli reaction catalyzed by ZnCl₂, whereas employment of Brønsted acid TFA afforded directly coupled product 3-(2-furyl)indoles in moderate to good yields (up to 87%) via the deprotonation-rearomatization route.

Direct C-2 acylation of indoles with toluene derivatives via Pd(ii)-catalyzed C–H activation

A simple and efficient Pd-catalyzed method for the C2-acylation of indoles is described using toluene derivatives.

Synthesis of Diketohexenoic Acid Derivatives by Alkenylation of Indoles and Pyrroles with 4-Pyrones

A new synthesis of functionalized (Z)-6-hetaryl-2,4-dioxo-5-hexenoic acids based on acid-catalyzed alkenylation of indoles and pyrroles with derivatives of 5-substituted 4-pyrone-2-carboxylic acid in 37-82% yields has been developed. Coupling between isochelidonic acid and indoles followed by decarboxylation afforded biologically important (E)-6-indolyl-2,4-dioxo-5-hexenoic acids. These ring-opening reactions proceed with high regioselectivity through nucleophilic attack at the C-6 position of the pyrone ring. Reactions of ethyl 6-indolyl-2,4-dioxo-5-hexenoate with nucleophiles are useful for the production of different β-(indolyl)vinyl-containing azaheterocycles.

Iron-catalyzed alkylation of α-oxo ketene dithioacetals

Iron-catalyzed alkylation of α-oxo ketene dithioacetals by styrenes efficiently afforded highly functionalized tetrasubstituted olefins.

FeCl3·6H2O catalyzed aqueous media domino synthesis of 5-monoalkylbarbiturates: water as both reactant and solvent

Water as both reactant and solvent in a FeCl₃·6H₂O catalyzed domino reaction towards 5-monoalkylbarbiturates is described.

Fe-catalyzed one-pot synthesis of 1,3-di- and 1,3,5-trisubstituted pyrazoles from hydrazones and vicinal diols

An iron-catalyzed route for the regioselective synthesis of 1,3- and 1,3,5-substituted pyrazoles from the reaction of diarylhydrazones and vicinal diols has been developed. This method was found to be practical with wide substrate scope.