Photoredox-Catalyzed Dimerization of Arylalkenes via an Oxidative [4+2] Cycloaddition Sequence: Synthesis of Naphthalene Derivatives

• Published in: Advanced synthesis & catalysis Vol. 358; no. 23; pp. 3887 - 3896
• Main Authors: Wei, Donglei, Li, Yanru, Liang, Fushun
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 07-12-2016
• Subjects: [4+2] cycloaddition; cascade reaction; Cycloaddition; Derivatives; Dimerization; Naphthalene; naphthalene derivatives; Organic chemistry; Photocatalysis; radical cations; Radicals; styrene derivatives; Synthesis (chemistry); visible light photocatalysis
• ISSN: 1615-4150; 1615-4169
• DOI: 10.1002/adsc.201600587

We report a radical cation [4+2] annulation of arylalkenes to afford naphthalene derivatives using an organic photosensitizer (9‐mesityl‐10‐methylacridinium perchlorate) under visible light photocatalysis. In the presence of oxygen (in the air), the oxidative dimerization/intramolecular [4+2] cycloaddition of two alkene molecules provides 3,4‐dihydronaphthalen‐1(2H)‐ones in good to high yields. Under a nitrogen atmosphere, (dihydro)naphthalenes were attained in moderate to excellent yields by using Selectfluor as the oxidant. The transformation proceeds via a tandem dimeric electrophilic addition/Friedel–Crafts cyclization/radical coupling/elimination sequence. This approach represents a mild and straightforward assembly of the naphthalene skeleton using a visible light photocatalytic cascade strategy.