Stabilising fleeting intermediates of stilbene photocyclization with amino-borane functionalisation: the rare isolation of persistent dihydrophenanthrenes and their [1, 5] H-shift isomers. Issue 15 (3rd April 2018)

• Record Type: Journal Article
• Authors: Shi, Yong-gang; Mellerup, Soren K.; Yuan, Kang; Hu, Guo-Fei; Sauriol, Francoise; Peng, Tai; Wang, Nan; Chen, Pangkuan; Wang, Suning
• Is Part Of: Chemical science. Volume 9:Issue 15(2018)
• Page Start: 3844
• Page End: 3855
• Publication Date: 2018-04-03
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c8sc00560e
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Amino-borane functionalization is the key for isolating rare air-stable dihydrophenanthrene intermediates in stilbene photocyclization. Abstract : The key intermediate, 4a, 4b-dihydrophenanthrene (DPH), involved in the photocyclization of stilbene and derivatives is known to be unstable, and is therefore poorly characterized/understood. We have found that functionalising stilbenes with NMe2 and BMes2 groups can greatly enhance the stability of 4a, 4b-DPHs, allowing quantitative isolation and full characterization of these rare species. Furthermore, we discovered that the new amino-borane decorated 4a, 4b-DPHs can undergo thermal [1, 5] H sigmatropic shift, forming isomers 4a, 10a-DPHs. Both 4a, 4b-DHPs and 4a, 10a-DHPs are stable towards air and moisture, while only the former were found to undergo oxidative dehydrogenation upon irradiation at 365 nm under air, yielding brightly blue/green fluorescent NMe2 and BMes2 functionalised phenanthrene analogues. Control studies established that the trans -Mes2 B–Ph–NMe2 unit is responsible for the stability of these isolated 4a, 4b-DHPs and their [1, 5]-H shift isomers.