Streamlined Synthesis of Varied Heteroarene-Condensed Benzofuran Derivatives via [4 + 2] Annulation of Benzofuran-Derived Azadienes and N-Alkyl Quinolinium Salts.

Herein we have pioneered an innovative synthetic strategy for the efficient assembly of various heteroarene-condensed benzofuran derivatives, utilizing benzofuran-derived azadienes (BDAs) and quinolines as the starting materials. This method functions with transition-metal catalysis and uses cost-effective formic acid as the reducing agent. Mechanistic investigations indicate that this transformation would involve a [4 + 2] annulation cascade process. This approach demonstrates a high tolerance to various functional groups and yields excellent results.

Efficient Functionalization of Organosulfones via Photoredox Catalysis: Direct Incorporation of α-Carbonyl Alkyl Side Chains into α-Allyl-ß-Ketosulfones.

A novel and efficient method for functionalizing organosulfones has been established, utilizing a visible-light-driven intermolecular radical cascade cyclization of α-allyl-ß-ketosulfones. This process employs fac-Ir(ppy)3 as the photoredox catalyst and α-carbonyl alkyl bromide as the oxidizing agent. Via this approach, the substrates experience intermolecular addition of α-carbonyl alkyl radicals to the alkene bonds, initiating a sequence of C-C bond formations that culminate in the production of organosulfone derivatives. Notably, this technique features gentle reaction conditions and an exceptional compatibility with a wide array of functional groups, making it a versatile and valuable addition to the field of organic synthesis.

Copper-catalyzed one-pot [3 + 2] cycloadditions of ethynyl indoloxazolidones with 1,3-cyclohexanediones.

Fused furans are commonly found units in natural products and medicinal molecules, and methods for their introduction are of fundamental importance. Here we report one-pot cycloadditions of ethynyl indoloxazolidones with 1,3-cyclohexanediones enabled by copper catalysis, leading to a series of functionalized furan derivatives in good yields. This method features mild reaction conditions, high efficiency, and wide substrate scope.

Brønsted acid-mediated tandem cyclization of triarylphosphines and in situ generated ortho-alkynyl quinone methides: access to heterocyclic quaternary phosphonium salts.

Heterocyclic Quaternary Phosphonium Salts (HQPS) have emerged as promising chemicals for organic synthesis and medicinal chemistry. However, the present synthetic methodology of this type of compound is still limited. Here, we report a deconstructive reorganization strategy based on Brønsted acid-mediated tandem 1,4 addition/intramolecular cyclization of triphenylphosphine derivatives and in situ generated o-AQMs for the first time. This protocol provides a novel approach to heterocyclic quaternary phosphonium salts. The method also features a non-metal catalyst, mild reaction conditions, high efficiency and wide substrate scope. Moreover, a series of obtained heterocyclic phosphonium salts can be converted to isotopically labelled 2-benzofuran compounds directly by simple deuteration reactions.

Preparation of Vinylphosphonates from Ketones Promoted by Tf2O.

An efficient triflic anhydride promoted phosphorylation of ketone was disclosed, and vinylphosphorus compounds were prepared under solvent- and metal-free conditions. Both aryl and alkyl ketones could perform smoothly to give vinyl phosphonates in high to excellent yields. In addition, the reaction was easy to carry out and easy to scale up. Mechanistic studies suggested that this transformation might involve nucleophilic vinylic substitution or a nucleophilic addition-elimination mechanism.

Markovnikov-addition of H-phosphonates to terminal alkynes under metal- and solvent-free conditions.

An addition of H-phosphonates to aryl alkynes was realized under solvent- and metal-free conditions, affording Markovnikov-selective α-vinylphosphonates in moderate to good yields. A wide range of aryl alkynes could be applied for the reaction. A tentative mechanism of addition-substitution was proposed based on in situ 31P {1H} NMR studies.