Stabilising fleeting intermediates of stilbene photocyclization with amino-borane functionalisation: the rare isolation of persistent dihydrophenanthrenes and their [1,5] H-shift isomers†,Chemical Science

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Stabilising fleeting intermediates of stilbene photocyclization with amino-borane functionalisation: the rare isolation of persistent dihydrophenanthrenes and their [1,5] H-shift isomers†
Chemical Science ( IF 7.6 ) Pub Date : 2018-03-27 00:00:00 , DOI: 10.1039/c8sc00560e
Yong-gang Shi _{1,

2,

3,

4,

5} , Soren K. Mellerup _{6,

7,

8,

9} , Kang Yuan _{6,

7,

8,

9} , Guo-Fei Hu _{1,

2,

3,

4,

5} , Francoise Sauriol _{6,

7,

8,

9} , Tai Peng _{1,

2,

3,

4,

5} , Nan Wang _{1,

2,

3,

4,

5} , Pangkuan Chen _{1,

2,

3,

4,

5} , Suning Wang _{1,

2,

3,

4,

5}

Affiliation

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-Mes₂B–Ph–NMe₂ unit is responsible for the stability of these isolated 4a,4b-DHPs and their [1,5]-H shift isomers.

中文翻译：

通过氨基硼烷官能化稳定二苯乙烯ene光环化的短暂中间体：持久性二氢菲及其[1,5] H位移异构体的稀有分离†

已知参与二苯乙烯和衍生物光环化的关键中间体4a，4b-二氢菲（DPH）是不稳定的，因此表征/理解较差。我们发现，使用NMe ₂和BMes ₂基团官能化的斯蒂苯类化合物可以大大增强4a，4b-DPHs的稳定性，从而可以对这些稀有物种进行定量分离和全面表征。此外，我们发现新的氨基硼烷修饰的4a，4b-DPHs可以经历热[1,5] H的σ位移，形成异构体4a，10a-DPHs。4a，4b-DHP和4a，10a-DHP均对空气和湿气稳定，而只有前者在空气中365 nm照射后会发生氧化脱氢，产生明亮的蓝色/绿色荧光NMe ₂和BMes ₂功能化的菲类似物。对照研究确定，反-Mes ₂ B–Ph–NMe ₂单元负责这些分离的4a，4b-DHP及其[1,5] -H转移异构体的稳定性。

更新日期：2018-03-27

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