Solvent-dependent oxidative coupling of 1-aryl-1,3-dicarbonyls and styrene

Reinventing the De Mayo reaction: synthesis of 1,5-diketones or 1,5-ketoesters via visible light [2+2] cycloaddition of β-diketones or β-ketoesters with styrenes

A visible light mediated De Mayo reaction between 1,3-diketones and styrenes following a [2+2] cycloaddition pathway via a photosensitization mechanism gives access to 1,5-diketones. The reaction has been applied to substituted styrenes and aryl- and alkyl-substituted ketones. Moreover, the method converts β-ketoesters, β-amido esters, and β-cyano ketones. Seven membered rings, a frequent structural motif of natural products, are also accessible using this methodology.

Tandem SN2' nucleophilic substitution/oxidative radical cyclization of aryl substituted allylic alcohols with 1,3-dicarbonyl compounds

A novel and efficient tandem S_N2' nucleophilic substitution/oxidative radical cyclization reaction of aryl substituted allylic alcohols with 1,3-dicarbonyl compounds has been developed by using Mn(OAc)₃ as an oxidant, which enables the expeditious synthesis of polysubstituted dihydrofuran (DHF) derivatives in moderate to high yields. The use of weakly acidic hexafluoroisopropanol (HFIP) as the solvent rather than AcOH has successfully improved the yields and expanded the substrate scope of this type of radical cyclization reactions. Mechanistic studies confirmed the cascade reaction process involving a final radical cyclization.

Cerium(IV) Tetrabutylammonium Nitrate (CTAN): A Mild and Efficient N-dearylation Agent for Synthesis of N-unsubstituted 2-azetidinones

A simple and efficient protocol for the conversion of N-p-methoxyphenyl, N-p-ethoxyphenyl, N-p-methoxynaphthyl, N-3,4-dimethoxybenzyl and N-p-methoxybenzyl-2-azetidinones to N-unsubstituted 2-azetidinones using cerium(IV) tetrabutylammonium nitrate (CTAN) in dichloromethane is described. The method is compatible with a number of functional groups, and N-unsubstituted 2-azetidinones can be prepared under mild conditions at room temperature. The reaction is rapid, and pure products are obtained in good yields.

Domino Radical Addition/Oxidation Sequence with Photocatalysis: One-Pot Synthesis of Polysubstituted Furans from α-Chloro-Alkyl Ketones and Styrenes

A new domino reaction has been developed that allows the combination of styrenes and α-alkyl ketone radicals to afford a wide array of polysubstituted furans in good to excellent yields under mild and simple reaction conditions. The key to success of this novel protocol is the use of photocatalyst fac-Ir(ppy)₃ and oxidant K₂ S₂ O₈ . Mechanistic studies by a radical scavenger and photoluminescence quenching suggest that a radical addition/oxidation pathway is operable.

A Copper-Catalyzed Formal [3 + 2]-Cycloaddition for the Synthesis of All Different Aryl-Substituted Furans and Thiophenes

A highly efficient formal [3 + 2]-cycloaddition was established using a copper catalyst. The resulting dihydrofurans were subjected to oxidation followed by arylations to produce tetraarylfurans. In addition, the dihydrofuran can be converted to diaryldihydrothiophene by using Lawesson's reagent. This protocol will facilitate the synthesis of all different aryl-substituted furans and thiophenes.

Mechanisms of Mn(OAc)(3)-based oxidative free-radical additions and cyclizations

The mechanistic details of Mn(OAc)(3)-based oxidative free-radical additions and cyclizations are reviewed. The mechanisms of electron transfer to generate radicals, electron transfer to convert the radicals to oxidized products, and further oxidation of the products are covered.