Cu(I)-Photosensitizer-Catalyzed Olefin-α-Amino Radical Metathesis/Demethylenative Cyclization of 1,7-Enynes.

A demethylenative En-Yne radical cyclization of 1,7-enynes has been successfully developed to chemoselectively afford 3,4-dihyroquinolin-2-ones or quinolin-2-ones under the catalysis of Cu(I) photosensitizers PS3 and PS6 with different redox potentials. The preliminary mechanistic experiments revealed that the reaction underwent an unprecedented olefin-α-amino radical metathesis-type process. A reasonable mechanism was proposed to illustrate the catalyst-controlled chemoselectivity of the reaction based on preliminary mechanistic experiments and DFT calculations.

P/N-heteroleptic Cu(I)-photosensitizer-catalyzed domino radical relay annulation of 1,6-enynes with aryldiazonium salts.

A visible-light driven photocatalytic construction of benzo[b]fluorenones from 1,6-enynes and aryldiazonium salts has been achieved via a P/N-heteroleptic Cu(I)-photosensitizer-catalyzed domino radical relay annulation process. Preliminary mechanistic studies revealed that the aryl radicals in situ generated from aryldiazonium salts with the excited state of the Cu(I)-photosensitizer played a dual role of a radical initiator and a radical terminator in the concise construction of the highly fused benzo[b]fluorenone scaffold.

Approach to Access Benzo[j]phenanthridinones from 1,7-Enynes and Aryldiazonium Salts via a Domino Radical Relay Process Enabled by a P/N-Heteroleptic Cu(I)-Photosensitizer.

A mild approach for the synthesis of benzo[j]phenanthridin-6(5H)-one derivatives from 1,7-enynes and aryldiazonium salts has been successfully developed involving a domino radical relay process enabled by a heteroleptic Cu(I)-photosensitizer under visible-light-driven photocatalytic conditions. Mechanistic studies disclosed that the oxidative quenching of the excited state of PS 4 with aryldiazonium salts via an SET process generated aryl radicals, which could play a radical initiator-terminator dual role within the whole radical relay process, namely, at the initial step acting as a radical donor to trigger the radical addition to the olefin moieties of 1,7-enynes while at the final stage serving as a radical acceptor to complete the cyclization.