The modulation of selectivity of highly reactive carbon radical cross-coupling for the construction of C–C bonds represents a challenging task in organic chemistry. N-Heterocyclic carbene (NHC) catalyzed radical transformations have opened a new avenue for acyl radical cross-coupling chemistry. With this method, highly selective cross-coupling of an acyl radical with an alkyl radical for efficient construction of C–C bonds was successfully realized. However, the cross-coupling reaction of acyl radicals with vinyl radicals has been much less investigated. We herein describe NHC and visible light-mediated photoredox co-catalyzed radical 1,4-sulfonylacylation of 1,3-enynes, providing structurally diversified valuable tetrasubstituted allenyl ketones. Mechanistic studies indicated that ketyl radicals are formed from aroyl fluorides via the oxidative quenching of the photocatalyst excited state, allenyl radicals are generated from chemo-specific sulfonyl radical addition to the 1,3-enynes, and finally, the key allenyl and ketyl radical cross-coupling provides tetrasubstituted allenyl ketones.

NHC and visible light-mediated photoredox co-catalyzed 1,4-sulfonylacylation of 1,3-enynes for tetrasubstituted allenyl ketones

A photocatalytic protocol for the synthesis of β-amino acid ester and β-amino ketone derivatives is developed by using simple and easy-to-synthesize oxime oxalate and oxime phenylglyoxylate as difunctionalization reagents. These...

Efficient Access to β-Amino Acid Ester/β-Amino Ketone Derivatives via Photocatalytic Radical Alkoxycabonylimidation/ Carbonylimidation of Alkenes

The multiple C-H bonds of biaryl ynones render the 6-exo-trig regioselective C-H activation dearomatization to spiro[5.5]trienones challenging since the competing reactions of C-H bonds on Ar1 or the ortho-C-H bonds on Ar3 may result in 5-exo-trig cyclization to indenones or 6-exo-trig ortho-dearomatization, respectively. We here report an unprecendented dearomatization of biaryl ynones with aldehydes via double C-H functionalization where a regiospecific remote unactivated para-C-H functionalization of biaryl ynones efficiently furnishes acylated spiro[5.5]trienones. This cascade cyclization features a green catalyst and solvent and high atom- and step-economy.

Iron-Catalyzed Dearomatization of Biaryl Ynones with Aldehydes via Double C-H Functionalization in Eco-Benign Solvents: Highly Atom-Economical Synthesis of Acylated Spiro[5.5]trienones.

The Dess-Martin periodinane (DMP) reagent-mediated reactions of tertiary enaminones with potassium thiocyanate for the synthesis of thiazole-5-carbaldehydes are developed. The product formation involves cascade hydroxyl thiocyanation of the C═C double bond, intramolecular hydroamination of the C≡N bond, and thiazole annulation by condensation on the ketone carbonyl site, representing novel reaction pathways in the reactions between enaminones and thiocyanate salt. DMP plays dual roles in mediating the free radical thiocyanation and inducing the unconventional selective thiazole-5-carbaldehyde formation by masking the in situ generated formyl group during the reaction process.

Yue-Jun Ouyang

Papers

Recent advances in acyl radical enabled reactions between aldehydes and alkenes