Origin of the Preferential Formation of Helicenes in Mallory Photocyclizations. Temperature as a Tool to Influence Reaction Regiochemistry
作者:J. Weber、E. L. Clennan
DOI:10.1021/acs.joc.8b02671
日期:2019.1.18
bis-Mallory photocyclization substrates has been examined from experimental and computational perspectives. Formation of all three possible regioisomers was only observed in the reaction of one of the substrates. In the other three substrates, only the two C2-symmetric products, but not the C1 product, were formed. In the three reactions that only formed two products, the photocyclization temperature
Expeditious synthesis of helicenes using an improved protocol of photocyclodehydrogenation of stilbenes
作者:Harish R. Talele、Anju R. Chaudhary、Parthiv R. Patel、Ashutosh V. Bedekar
DOI:10.3998/ark.5550190.0012.902
日期:——
developed for photodehydrocyclization of stilbenes for the synthesis of phenanthrenes and helicenes. This procedure involves the use of THF as a scavenger of hydriodicacid produced during iodine mediated photodehydrocyclization. The use of THF is advantageous due to its higher boiling point, lower cost and easy availability as compared to propylene oxide. The method is applied to synthesize a number
Systematic investigations on fused π-system compounds of seven benzene rings prepared by photocyclization of diphenanthrylethenes
作者:Shota Fujino、Minoru Yamaji、Hideki Okamoto、Toshiki Mutai、Isao Yoshikawa、Hirohiko Houjou、Fumito Tani
DOI:10.1039/c7pp00040e
日期:2017.6
(nEm; n, m = 1, 3 and 9) for understanding photocyclization patterns based on NMR spectroscopy. The crystal structures of the photoproducts were analyzed by X-ray crystallography, and the photophysical features of the photocyclized molecules were investigated based on emission and transient absorptionmeasurements. Phenanthrene derivatives substituted at the 1- and 3-positions were prepared for synthesizing
我们研究了1-(n-菲基)-2-(m-菲基)乙烯的光产物(n E m;n,m = 1、3和9),以了解基于NMR光谱的光环化模式。通过X射线晶体学分析光产物的晶体结构,并基于发射和瞬态吸收测量来研究光环化分子的光物理特征。制备了在1-位和3-位取代的菲衍生物,用于通过二苯乙烯衍生物的光环化合成n E m。我们获得了四种主要的光产品(n @ m)从相应的n E m。通过X射线晶体学测定,发现其中两个在单晶中具有外消旋分子结构。除了主要的光产物外,还分离出两种类型的次要光产物(n @ m PP)。在溶液中测定了获得的光产物的荧光量子产率和寿命,而在粉末中获得了确定的荧光量子产率。通过激光光解技术观察溶液中的三重态-三重态吸收光谱表明,跨系统进入三重态的过程与荧光过程竞争。
Photodehydrocyclizations in stilbene-like compounds—III
作者:W.H. Laarhoven、T.H.J.H.M. Cuppen、R.J.F. Nivard
DOI:10.1016/s0040-4020(01)93139-4
日期:1970.1
Photodehydrocyclizations in stilbene-like compounds take place only if the sum of the free valence numbers of the atoms concerned in the cyclization step exceeds in the excited state, a value of 1. If more than one cyclization is possible the photoconversion follows the pathway for which ΣF* is maximal; if ΔΣF* for various cyclizations is smaller than 0·1 a second product is sometimes formed.