Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Main Authors: Hai Ming Wang, Gerhard Wenz
• Format: Article
• Language: English
• Published: Beilstein-Institut 2013-09-01
• Series: Beilstein Journal of Organic Chemistry
• Subjects: acenaphthylene; anthracene; coumarin; cyclodextrins; photodimerization; quantum yield; stereoselectivity
• Online Access: https://doi.org/10.3762/bjoc.9.217

The formation of soluble 1:2 complexes within hydrophilic γ-cyclodextrin (γ-CD) thioethers allows to perform photodimerizations of aromatic guests under controlled, homogenous reaction conditions. The quantum yields for unsubstituted anthracene, acenaphthylene, and coumarin complexed in these γ-CD thioethers were found to be up to 10 times higher than in the non-complexed state. The configuration of the photoproduct reflected the configuration of the dimeric inclusion complex of the guest. Anti-parallel orientation of acenaphthylene within the CD cavity led to the exclusive formation of the anti photo-dimer in quantitative yield. Parallel orientation of coumarin within the complex of a CD thioether led to the formation of the syn head-to-head dimer. The degree of complexation of coumarin could be increased by employing the salting out effect.