Cu(II)-Catalyzed 6π-Photocyclization of Non-6π Substrates

Abstract

This research successfully achieved a Cu­(II)-catalyzed 6π-photocyclization of non-6π substrates. The photoenolization converts ortho-alkylphenyl alkynl ketones into a triene-type intermediate which undergoes the subsequent 6π-photocyclization to give naphthol as the final product. Cu­(II) catalyst facilitates both photoenolization and 6π-photocyclization. This research highlighted the tandem reaction strategy and the importance of metal catalysis in photochemistry.

Palladium-Catalyzed Regiospecific peri- and ortho-C–H Oxygenations of Polyaromatic Rings Mediated by Tunable Directing Groups

“…To save the additional assembly/disassembly of directing groups in this strategy, a transient directing group (TDG, Figure a) strategy that links the substrates reversibly in situ to chelate the C–H metalation was pioneered by the Yu group and extensively exploited to a wide array of aldehyde, − ketone, , and amines. − Phenylation, succinylation, and halogenation of benzene rings directed by the TDG strategy have occasionally stretched to polyaromatic examples . However, practical regioselective synthetic methods to access the site-specific oxygenation of polyaromatic rings represented by naphthalene are underdeveloped, and there is a disparity in step-economical efficiency of existing approaches as exemplified by the syntheses starting from various aromatic ketones (Figure b) …”

Visible‐Light‐Driven Cyclizations

“…In 2020, Hao Guo reported a Cu II 6p–photocyclization of non 6p–substrates [254] . As can be seen in Scheme 166, the reaction starts with the coordination of Cu II to the alkyne moiety of substrate 852 .…”

Substituted Naphthols: Preparations, Applications, and Reactions

“…In 2020, Guo and colleagues discovered that copper(II) activation of alkyne moieties in ortho ‐alkylphenyl alkynl ketones 54 allowed the formation of trienes 56 after a light induced photo‐enolization – this resulting species 56 could then undergo a 6π‐photo‐cyclization reaction to access substituted 1‐naphthol products 57 (Scheme 10, 22 examples, yields ranging between 71 %‐94 %). [ 55 ] The copper(II) catalyst was found to be integral in both the photoenolization and 6π‐photocyclization steps; moreover, in its absence, unidentifiable decomposition of the starting material was observed (moreover, in the absence of purple LED light, only starting material was recovered).…”