Photomediated Spirocyclization of N-Benzyl Propiolamide with N-Iodosuccinimide for Access to Azaspiro[4.5]deca-6,9-diene-3,8-dione

A metal- and oxidant-free route for affording azaspiro[4.5]deca-6,9-diene-3,8-dione via photomediated iodinated spirocyclization of N-(4-methoxybenzyl) propiolamide has been developed. The reaction underwent a radical addition/ipso-cyclization/dearomatization process at room temperature and successfully constructed C-C and C-I bonds. This green and convenient approach could be generally expanded to produce a range of iodinated spirocyclization products in moderate to good yields.

A simple approach to C3-ethoxycarbonylmethylation of thiophenes/furans with diethyl bromomalonate

A mild and efficient method to produce C3-malonated products was developed via a visible-light-induced radical reaction of 2-substituted thiophenes/furans with diethyl bromomalonate. The C3-ethoxycarbonylmethylation of 2-substituted thiophenes/furans exhibited broad substrate...

A visible-light-induced photocatalyst-free approach for C-3 dicarbonyl coumarin production

A mild and efficient visible-light-induced synthesis of C-3 dicarbonyl coumarins from 3-arylacetylene coumarins without a photocatalyst was reported. This iodide-mediated method exhibited broad substrate scope and good functional group tolerance, and a series of C-3 dicarbonyl coumarins were obtained in moderate to excellent yields. Based on the control experimental results, it was found that the visible-light-induced oxidation might be via both radical and ionic processes. Moreover, some synthesized compounds displayed high sensitivity to hydrogen peroxide (H₂O₂) with a low detection limit (DL, down to 0.149 μM).

An electrolyte- and catalyst-free electrooxidative sulfonylation of imidazo[1,2-a]pyridines

An electrolyte- and catalyst-free electrooxidative C–H activation reaction is developed to afford 3-sulfonylated imidazo[1,2-a]pyridines in good to excellent yields.

A computational study for the reaction mechanism of metal-free cyanomethylation of aryl alkynoates with acetonitrile

A computational study of metal-free cyanomethylation and cyclization of aryl alkynoates with acetonitrile is carried out employing density functional theory and high-level coupled-cluster methods, such as coupled-cluster singles and doubles with perturbative triples [CCSD(T)]. Our results indicate that the reaction of aryl alkynoates with acetonitrile in the presence of tert-butyl peroxybenzoate (TBPB) under metal-free conditions tends to proceed through cyanomethylation, spirocyclization and ester migration of the kinetically favoured coumarin derivatives. 1,2-Ester migration in the spiro-radical intermediate 10 does not proceed via the formation of the carboxyl radical 11 suggested by Sun and co-workers. Our results also demonstrate that the t-butoxy radical is substantially responsible the formation of the cyanomethyl radical by the abstraction of a hydrogen atom from acetonitrile.

A computational study of metal-free cyanomethylation and cyclization of aryl alkynoates with acetonitrile is carried out employing density functional theory and high-level coupled-cluster methods, such as [CCSD(T)].

"One-Pot" Synthesis of γ-Pyrones from Aromatic Ketones/Heteroarenes and Carboxylic Acids

Despite the various attractive properties of γ-pyrones, there are still some deficiencies in their synthetic approaches such as lower atom economy, multistep processes, and prefunctionalization of the reagents. In this work, an efficient and simple (CF₃CO)₂O/CF₃SO₃H-mediated "one-pot" approach was realized to produce γ-pyrones by applying aromatic ketones/heteroarenes and carboxylic acids as the starting materials. The target products were isolated in moderate to excellent yields. The reaction mechanism was studied by density functional theory calculational methods. The results of experimental and theoretical investigations not only helped us explain the reason of high selectivity formation of β-diketones but also proved that 1,3,5-ketones might be important intermediates for the cyclization to afford γ-pyrones.