Synthesis of 6 H-Benzo[ c]chromene Scaffolds from O-Benzylated Phenols through a C-H Sulfenylation/Radical Cyclization Sequence
S-Aryl dibenzothiophenium salts, obtained through a highly regioselective C-H sulfenylation of o-benzyl-protected phenols, are used as precursors of 6H-benzo[c]chromenes. The reaction starts with a photocatalytically triggered single-electron transfer to the sulfonium salt, which promotes the formation of an aryl radical via selective mesolitic cleavage of the S-Arexo bond. Mechanistic studies reveal that this initial radical species cyclizes following a kinetically favored 5-exo-trig pathway. Subsequent ring expansion, favored by rearomatization, delivers the desired tricyclic systems.
Karreman, Steve,Karnbrock, Simon B. H.,Kolle, Sebastian,Golz, Christopher,Alcarazo, Manuel
Mild environment-friendly oxidative debenzylation of N-benzylanilines using DMSO as an oxidant
Oxidative debenzylation of N-benzyl aromatic amines using DMSO as a non-toxic oxidant and catalyzed by TsOH gave Nphenylimines, which were spontaneously hydrolyzed to form anilines and benzaldehydes in good yields. This reaction employs mild, metal-free conditions. The conditions are also suitable for the debenzylation of benzylphenylethers.