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.