Photocatalytic xanthate-based radical addition/cyclization reaction sequence toward 2-biphenyl isocyanides: synthesis of 6-alkylated phenanthridines

Electro-oxidative Methylation of 2-Isocyanobiaryls Using N,N-dimethylformamide (DMF) as Carbon Source: Synthesis of 6-Methylphenanthridines

A benign electrochemical method to access 6-methylphenanthridines from 2-isocyanobiaryls using N,N-dimethylformamide (DMF) as a methyl source is reported. The protocol operates at ambient temperature without the need for harmful methylating reagents. Mechanistic studies suggested that DMF delivered a methylene synthon, followed by reduction at the cathode and tautomerization. The method offers environmental benefits by avoiding metal-based reagents and harsh conditions.

Electrochemical trifluoromethylation of 2-isocyanobiaryls using CF3SO2Na: synthesis of 6-(trifluoromethyl)phenanthridines

An efficient trifluoromethylation of 2-isocyanobiaryls was developed through the constant current electrolysis, employing sodium trifluoromethanesulfinate (CF₃SO₂Na) as the trifluoromethyl source. The method enabled the syntheses of a series of 6-(trifluoromethyl)phenanthridine derivatives in moderate to high yields under metal- and oxidant-free conditions. A gram-scale synthesis highlights the synthetic versatility of the reported protocol.

Synthesis of Sulfur-Containing Oxindoles by Photoinduced Alkene Difunctionalization via Sulfur 1,2-Relocation

Organosulfur compounds are prevalent in various natural products, which have been widely applied in agrochemicals and pharmaceuticals. Herein, a new approach for the efficient construction of sulfur-containing oxindoles by photoinduced alkene difunctionalization via sulfur 1,2-relocation is developed. The method exhibited a high functional group tolerance and broad substrate compatibility. A library of sulfur-containing oxindole derivatives were synthesized under mild conditions (metal-, photocatalyst-, and additive-free). Mechanistic investigations revealed this photochemical process was triggered by the formation of an EDA complex of oxindole enolates with a redox-active ester, and the in situ generation of alkenes from the C-S bond cleavage of β-sulfanyl radicals was a key step in this transformation.

α-Xanthylmethyl Ketones from α-Diazo ketones

A simple and efficient method to obtain α-xanthylmethyl ketones from α-diazo ketones is described. The reaction proceeds through a protonation/nucleophilic substitution sequence in the presence of p-toluenesulfonic acid and potassium ethyl xanthogenate as the nucleophile. As α-diazo ketones can be readily synthesized from ubiquitous carboxylic acids, a broad variety of xanthates can be obtained, including examples from naturally occurring substrates.

Recent advances in cascade radical cyclization of radical acceptors for the synthesis of carbo- and heterocycles

This review is devoted to highlighting main achievements in the development of cascade radical cyclization of radical acceptors for the synthesis of carbo- and heterocycles.

Hantzsch Ester-Mediated Synthesis of Phenanthridines under Visible-Light Irradiation

An efficient photocatalytic synthesis of phenanthridines mediated by an organo-photoredox initiator Hantzsch ester has been developed via denitrogenative intramolecular annulation of benzotriazolyl chalcones. The highly reducing photoactivated Hantzsch ester facilitates the transformation of benzotriazolyl chalcones into phenanthridinyl chalcones through photoinduced electron transfer (PET) and hydrogen atom transfer (HAT) processes. The mild reaction conditions utilizing inexpensive Hantzsch ester as photosensitizer, wide reaction scope and excellent functional group tolerance are notable attributes of the methodology.