Concise [4+3] cycloaddition reaction of pyrroles leading to tropinone derivatives

Stereoselective (4 + 3) cycloadditions of allenyl ethers-furans by chiral auxiliaries inducing and evaluation of anti-breast cancer activity

The medicinal plants were wildly library of natural products in drug discovery. The most active molecules with seven-membered rings skeleton represent a challenge for construction. A stereoselectivity (4 + 3) cycloadditions between allenyl ethers and substituted furans induced by chiral auxiliaries has been investigated. And the results showed significant stereoselectivities and regioselectivities. The optical cycloadducts with an oxygen-substituted seven-membered ring framework were generated by removing chiral auxiliaries under acidic conditions. The antiproliferative activity of the novel compounds displayed moderate antiproliferative effects toward T47D cells.

(4 + 3) cycloadditions of allenyl ether-derived oxygen-stabilized oxyallyls with furans

(4 + 3) Cycloadditions between allenyl ethers and furans are described. The reaction features anin situformation of oxygen-stabilized oxyallylsviaepoxidations of allenyl ethers in the presence of H₂PO₄⁻.

Retracted Article: An efficient one pot three-component synthesis of 2,4,6-triarylpyridines using triflimide as a metal-free catalyst under solvent-free conditions

A simple and efficient protocol developed for one pot three-component synthesis of 2,4,6-triarylpyridines from aromatic aldehydes, substituted acetophenones and ammonium acetate using the versatile super Brønsted acid triflimide (HNTf₂) as an effective catalyst is described. The reactions proceed well in the presence of 1 mol% of HNTf₂ at 80 °C under solvent-free conditions and provide the corresponding triarylpyridines in good to excellent yields. The method reported has several advantages such as a metal-free and commercially available catalyst, mild reaction conditions and lower loading of catalyst.

A simple and efficient protocol developed for one pot three-component synthesis of 2,4,6-triarylpyridines from aromatic aldehydes, substituted acetophenones and ammonium acetate using triflimide (HNTf₂) as an effective catalyst is described.

Direct Synthesis of Polycyclic Tropinones by a Condensation-[4+3]-Cycloaddition Cascade Reaction

A concise method of constructing polycyclic tropinone frameworks was developed. The single-step synthesis of polycyclic tropinone consists of an intramolecular [4+3] cycloaddition reaction of N-nosyl-pyrrole with oxyallyl cation that was generated in situ by an intermolecular condensation reaction of the nucleophilic functional groups on a tethered pyrrole with the aldehyde of 2-(silyloxy)-acrolein. This cascade reaction afforded various polycyclic tropinones including tri-, tetra-, and pentacyclic systems in high yields as single diastereomers.

Intramolecular (4+3) Cycloadditions of Pyrroles and Application to the Synthesis of the Core of Class II Galbulimima Alkaloids

The first intramolecular (4+3) cycloaddition of pyrroles with epoxy enolsilanes as the electrophiles was developed and used to generate optically-enriched cycloadducts containing the nortropane substructure in good yields. Using this pyrrole cycloaddition as the key step, we achieved the asymmetric synthesis of a nortropane compound bearing the BCDEF ring structure common to the Class II galbulimima alkaloids.

Application of (4+3) cycloaddition strategies in the synthesis of natural products

This review summarizes the applications of (4+3) cycloadditions, both classical and formal, in the syntheses of natural products in the last two decades.