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.

Single Cu(I)-Photosensitizer Enabling Combination of Energy-Transfer and Photoredox Catalysis for the Synthesis of Benzo[b]fluorenols from 1,6-Enynes.

An efficient, mild, and atom-economical synthesis of benzo[b]fluorenols from 1,6-enynes has been developed under photocatalytic conditions. A single P/N heteroleptic Cu(I)-photosensitizer might exhibit both energy-transfer and photoredox catalytic activities in the formation of benzo[b]fluorenols.

Tertiary Amines Acting as Alkyl Radical Equivalents Enabled by a P/N Heteroleptic Cu(I) Photosensitizer.

An unprecedented exploration of tertiary amines as alkyl radical equivalents for cross-coupling with aromatic alkynes to access allylarenes has been achieved by a P/N heteroleptic Cu(I)-based photosensitizer under photoredox catalysis conditions. Mechanistic studies reveal that the reaction might undergo radical addition of in situ-generated α-amino radical intermediates to alkynes followed by 1,5-hydrogen transfer, C-N bond cleavage, and concomitant isomerization of the resulting allyl radical species.

Radical-Triggered Tandem Cyclization of 1,6-Enynes with H2O: A Way to Access Strained 1 H-Cyclopropa[ b]naph thalene-2,7-diones.

A radical-triggered tandem cyclization of 1,6-enynes has been developed herein. Strained 1 H-cyclopropa[ b]naphthalene-2,7-diones are successfully obtained in moderate to good yields with excellent stereoselectivity. Mechanistic studies reveal a key role of water in generating a hydroxyl radical that initiates a sequential Michael addition/ring closure pathway. Importantly, the formed hydroxyl is proposed to be a good leaving group during the cyclopropane ring formation.